U.S. patent number 11,097,974 [Application Number 15/749,015] was granted by the patent office on 2021-08-24 for thermally strengthened consumer electronic glass and related systems and methods.
This patent grant is currently assigned to Corning Incorporated. The grantee listed for this patent is Corning Incorporated. Invention is credited to Peter Joseph Lezzi, Richard Orr Maschmeyer, John Christopher Thomas, Kevin Lee Wasson.
United States Patent |
11,097,974 |
Lezzi , et al. |
August 24, 2021 |
Thermally strengthened consumer electronic glass and related
systems and methods
Abstract
A strengthened cover glass or glass-ceramic sheet or article as
well as processes and systems for making the strengthened glass or
glass-ceramic sheet or article is provided for use in consumer
electronic devices. The process comprises cooling the cover glass
sheet by non-contact thermal conduction for sufficiently long to
fix a surface compression and central tension of the sheet. The
process results in thermally strengthened cover glass sheets for
use in or on consumer electronic products.
Inventors: |
Lezzi; Peter Joseph (Corning,
NY), Maschmeyer; Richard Orr (Corning, NY), Thomas; John
Christopher (Elmira, NY), Wasson; Kevin Lee (Elmira,
NY) |
Applicant: |
Name |
City |
State |
Country |
Type |
Corning Incorporated |
Corning |
NY |
US |
|
|
Assignee: |
Corning Incorporated (Corning,
NY)
|
Family
ID: |
78414086 |
Appl.
No.: |
15/749,015 |
Filed: |
July 28, 2016 |
PCT
Filed: |
July 28, 2016 |
PCT No.: |
PCT/US2016/044406 |
371(c)(1),(2),(4) Date: |
January 30, 2018 |
PCT
Pub. No.: |
WO2017/019840 |
PCT
Pub. Date: |
February 02, 2017 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20190002331 A1 |
Jan 3, 2019 |
|
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
14814232 |
Jul 30, 2015 |
9296638 |
|
|
|
14814274 |
Jul 30, 2015 |
9776905 |
|
|
|
14814293 |
Jul 30, 2015 |
9802853 |
|
|
|
14814303 |
Jul 30, 2015 |
9783448 |
|
|
|
14814363 |
Jul 30, 2015 |
10005691 |
|
|
|
14814319 |
Jul 30, 2015 |
9975801 |
|
|
|
14814335 |
Jul 30, 2015 |
10077204 |
|
|
|
62286192 |
Jan 22, 2016 |
|
|
|
|
62288851 |
Jan 29, 2016 |
|
|
|
|
62236296 |
Oct 2, 2015 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C03B
29/16 (20130101); B32B 17/10119 (20130101); C03C
21/002 (20130101); C03B 35/24 (20130101); C03B
27/016 (20130101); C03B 27/012 (20130101); C03B
27/0413 (20130101); C03C 23/007 (20130101); G06F
3/041 (20130101); C03B 27/048 (20130101); B32B
17/10091 (20130101); B60J 1/001 (20130101); C03B
27/044 (20130101); C03B 27/04 (20130101); C03B
27/052 (20130101); G06F 3/016 (20130101); C03B
29/12 (20130101); B32B 17/10036 (20130101); C03B
27/0526 (20130101); C03B 27/0404 (20130101); B32B
17/101 (20130101); C03C 3/11 (20130101); Y10T
428/315 (20150115); Y02P 40/57 (20151101); B32B
2307/538 (20130101) |
Current International
Class: |
C03B
27/012 (20060101); C03B 29/16 (20060101); C03B
29/12 (20060101); B60J 1/00 (20060101); B32B
17/10 (20060101); C03B 27/016 (20060101); C03C
21/00 (20060101); C03C 3/11 (20060101); C03B
27/048 (20060101); C03B 27/044 (20060101); C03B
27/04 (20060101); C03B 35/24 (20060101); C03B
27/052 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
4265772 |
|
Nov 1973 |
|
AU |
|
535129 |
|
Jan 1984 |
|
AU |
|
1208266 |
|
Jun 2005 |
|
CN |
|
101671112 |
|
Mar 2010 |
|
CN |
|
102659305 |
|
Sep 2012 |
|
CN |
|
103253857 |
|
Aug 2013 |
|
CN |
|
103319082 |
|
Sep 2013 |
|
CN |
|
103359934 |
|
Oct 2013 |
|
CN |
|
103781733 |
|
May 2014 |
|
CN |
|
104211288 |
|
Dec 2014 |
|
CN |
|
104260569 |
|
Jan 2015 |
|
CN |
|
104310773 |
|
Jan 2015 |
|
CN |
|
104355530 |
|
Feb 2015 |
|
CN |
|
104479282 |
|
Apr 2015 |
|
CN |
|
106045283 |
|
Oct 2016 |
|
CN |
|
2233057 |
|
Mar 1973 |
|
DE |
|
0173418 |
|
Mar 1986 |
|
EP |
|
2853517 |
|
Apr 2015 |
|
EP |
|
2326386 |
|
Apr 1977 |
|
FR |
|
1103192 |
|
Feb 1968 |
|
GB |
|
1160284 |
|
Aug 1969 |
|
GB |
|
1289488 |
|
Sep 1972 |
|
GB |
|
2232978 |
|
Jan 1991 |
|
GB |
|
200301606 |
|
Apr 2006 |
|
IN |
|
51103920 |
|
Sep 1976 |
|
JP |
|
55104935 |
|
Aug 1980 |
|
JP |
|
56155030 |
|
Dec 1981 |
|
JP |
|
56155031 |
|
Dec 1981 |
|
JP |
|
57067035 |
|
Apr 1982 |
|
JP |
|
57067036 |
|
Apr 1982 |
|
JP |
|
58088132 |
|
May 1983 |
|
JP |
|
58091042 |
|
May 1983 |
|
JP |
|
598626 |
|
Jan 1984 |
|
JP |
|
598627 |
|
Jan 1984 |
|
JP |
|
598628 |
|
Jan 1984 |
|
JP |
|
598629 |
|
Jan 1984 |
|
JP |
|
598630 |
|
Jan 1984 |
|
JP |
|
598631 |
|
Jan 1984 |
|
JP |
|
59057923 |
|
Apr 1984 |
|
JP |
|
60171245 |
|
Sep 1985 |
|
JP |
|
62036030 |
|
Feb 1987 |
|
JP |
|
63270330 |
|
Nov 1988 |
|
JP |
|
02175624 |
|
Jul 1990 |
|
JP |
|
02102436 |
|
Aug 1990 |
|
JP |
|
03045526 |
|
Feb 1991 |
|
JP |
|
03271127 |
|
Dec 1991 |
|
JP |
|
07157322 |
|
Jun 1995 |
|
JP |
|
07267664 |
|
Oct 1995 |
|
JP |
|
2000072463 |
|
Mar 2000 |
|
JP |
|
2000103632 |
|
Apr 2000 |
|
JP |
|
2000172202 |
|
Jun 2000 |
|
JP |
|
2000327355 |
|
Nov 2000 |
|
JP |
|
2001307662 |
|
Nov 2001 |
|
JP |
|
2003040635 |
|
Feb 2003 |
|
JP |
|
2003137603 |
|
May 2003 |
|
JP |
|
2003261344 |
|
Sep 2003 |
|
JP |
|
2003342030 |
|
Dec 2003 |
|
JP |
|
2007191319 |
|
Aug 2007 |
|
JP |
|
2007261850 |
|
Oct 2007 |
|
JP |
|
4642107 |
|
Mar 2011 |
|
JP |
|
4722371 |
|
Jul 2011 |
|
JP |
|
4951838 |
|
Jun 2012 |
|
JP |
|
2015086080 |
|
May 2015 |
|
JP |
|
100218143 |
|
Sep 1999 |
|
KR |
|
20020061567 |
|
Jul 2002 |
|
KR |
|
100690381 |
|
Mar 2007 |
|
KR |
|
100918577 |
|
Sep 2009 |
|
KR |
|
100937889 |
|
Jan 2010 |
|
KR |
|
101000677 |
|
Dec 2010 |
|
KR |
|
101032825 |
|
May 2011 |
|
KR |
|
20110087774 |
|
Aug 2011 |
|
KR |
|
20110106629 |
|
Sep 2011 |
|
KR |
|
20110112503 |
|
Oct 2011 |
|
KR |
|
101093947 |
|
Dec 2011 |
|
KR |
|
101120262 |
|
Mar 2012 |
|
KR |
|
20120051220 |
|
May 2012 |
|
KR |
|
20120070450 |
|
Jun 2012 |
|
KR |
|
101248380 |
|
Mar 2013 |
|
KR |
|
101286131 |
|
Jul 2013 |
|
KR |
|
20130024484 |
|
Sep 2014 |
|
KR |
|
20140110364 |
|
Sep 2014 |
|
KR |
|
2151750 |
|
Jun 2000 |
|
RU |
|
2199496 |
|
Feb 2003 |
|
RU |
|
2237621 |
|
Oct 2004 |
|
RU |
|
2299184 |
|
May 2007 |
|
RU |
|
2464243 |
|
Oct 2012 |
|
RU |
|
254731 |
|
Mar 2013 |
|
RU |
|
95854 |
|
Nov 1952 |
|
SU |
|
443845 |
|
Sep 1974 |
|
SU |
|
537960 |
|
Dec 1976 |
|
SU |
|
631464 |
|
Nov 1978 |
|
SU |
|
556593 |
|
Aug 1982 |
|
SU |
|
548188 |
|
Sep 1982 |
|
SU |
|
1098916 |
|
Jun 1984 |
|
SU |
|
1150234 |
|
Apr 1985 |
|
SU |
|
1655920 |
|
Jun 1991 |
|
SU |
|
1990003337 |
|
Apr 1990 |
|
WO |
|
2002016277 |
|
Mar 2001 |
|
WO |
|
2003014035 |
|
Feb 2003 |
|
WO |
|
2006110145 |
|
Oct 2006 |
|
WO |
|
2008020509 |
|
Feb 2008 |
|
WO |
|
2012142629 |
|
Oct 2012 |
|
WO |
|
2014139147 |
|
Sep 2014 |
|
WO |
|
2014201315 |
|
Dec 2014 |
|
WO |
|
2015031594 |
|
Mar 2015 |
|
WO |
|
2016019171 |
|
Feb 2016 |
|
WO |
|
2016183059 |
|
Nov 2016 |
|
WO |
|
2017020041 |
|
Feb 2017 |
|
WO |
|
Other References
Boaz, "Tempering very thin glass; what radio waves mean for the
glass industry," USGlass, vol. 45, issue 3. (Year: 2010). cited by
examiner .
Deschamps, T. et al., "Soda-lime silicate glass under hydrostatic
pressure and indentation: a micro-Raman study," Abstract, 2011, 1
page. cited by applicant .
Deschamps, T. et al., "Soda-lime silicate glass under hydrostatic
pressure and indentation: a micro-Raman study," Journal of Physics:
Condensed Matter, vol. 23, 2011, 7 pages. cited by applicant .
Donald, I. W., "Review: Methods for improving the mechanical
properties of oxide glasses," Journal of Materials Science, vol.
24, 1989, pp. 4177-4208. cited by applicant .
Electronic Cooling Editors, "The Thermal Conductivity of Gases",
Design, Materials, Adhesives, Substrates, No. 3, Technical Data,
Test & Measurement, vol. 4, Gases, Thermal Conductivity, 2
pages. cited by applicant .
Ernsberger, F. M., "Chapter 1: Elastic Properties of Glasses," in
"Glass: Science and Technology," vol. 5, Elasticity and Strength in
Glasses, Academic Press, Inc., May 28, 1980, pp. 1-19. cited by
applicant .
Ernsberger, F. M., "Chapter 4: Techniques of Strengthening
Glasses," in "Glass: Science and Technology," vol. 5, Elasticity
and Strength in Glasses, Academic Press, Inc., May 28, 1980, pp.
133-144. cited by applicant .
Europtec; "Themal Tempering"; Europtec Gmbh, DIC, Jun. 11, 2014;
www.europtec.de. cited by applicant .
Everall, Neil et al., "Optimizing Depth Resolution in Confocal
Raman Microscopy: A Comparison of Metallurgical, Dry Corrected, and
Oil Immersion Objectives," Applied Sprectroscopy, vol. 61, No. 3,
2007, pp. 251-259. cited by applicant .
Everall, Neil J., "Confocal Raman Microscopy: Why the Depth
Resolution and Spatial Accuracy Can Be Much Worse then You Think,"
Applied Spectroscopy, vol. 54, No. 10, 2000, pp. 1515-1520. cited
by applicant .
Fajans, Kasi Mir et al., "Properties and Structures of Vitreous and
Crystalline Boron Oxide," Journal of the American Chemical Society,
vol. 74, No. 11, Jun. 5, 1952, pp. 2761-2768. cited by applicant
.
Fotheringham, Dr. Ulrich, "Lecture 1: Internet teaching set-up,"
IMI-NFG's MITT Course on Relaxation Processes in Glass and Polymers
Lecture 1, 2010, 6 slides. cited by applicant .
Fotheringham, Dr. Ulrich, "Lecture 2: Phenomenology of
viscoelasticity & glass transition," IMI-NFG's MITT Course on
Relaxation Processes in Glass and Polymers Lecture 2, 2010, 17
slides. cited by applicant .
Fotheringham, Dr. Ulrich, "Lecture 5: Viscoelasticity I--Shear,"
IMI-NFG's MITI Course on Relaxation Processes in Glass and Polymers
Lecture 5, 2010, 19 slides. cited by applicant .
Fotheringham, Dr. Ulrich, "Lecture 6: Viscoelasticity II--Bulk
Viscoelasticity," IMI-NFG's MITI Course on Relaxation Processes in
Glass and Polymers Lecture 6, 2010, 16 slides. cited by applicant
.
Fotheringham, Dr. Ulrich, "Lecture 7: Viscoelasticity III--Dynamic
Testing," IMI-NFG's MITI Course on Relaxation Processes in Glass
and Polymers Lecture 7, 2010, 19 slides. cited by applicant .
Fotheringham, Dr. Ulrich, "Lecture 8: Viscoelasticity IV--Important
Application of Pre-Stressing," IMI-NFG's MITT Course on Relaxation
Processes in Glass and Polymers Lecture 8, 2010, 12 slides. cited
by applicant .
Freiman, S. W., "Chapter 2: Fracture Mechanics of Glass," in
"Glass: Science and Technology," vol. 5, Elasticity and Strength in
Glasses, Academic Press, Inc., May 28, 1980, pp. 21-78. cited by
applicant .
Frick, B. et al., "The Microscopic Basis of the Glass Transition in
Polymers from Neutron Scattering Studies," Science, vol. 267, Mar.
31, 1995, pp. 1939-1945. cited by applicant .
Galeener, Frankl., "Raman and ESR Studies of the Thermal History of
Amorphous Si02," Journal of Non-Crystalline Solids, vol. 71, 1985,
pp. 373-386. cited by applicant .
Gang, Zhang Ming, "Manufacturing and Properties of Glass Used in
Construction," Guangdong Golden Glass Technologies Ltd, Dec. 27,
2002, 11 pages. cited by applicant .
Gardon, Robert, "Calculation of Temperature Distributions in Glass
Plates Undergoing Heat-Treatment," Journal of the American Ceramic
Society, vol. 41, No. 6, Jun. 1958, pp. 200-209. cited by applicant
.
Gardon, Robert, "Chapter 5: Thermal Tempering of Glass," in "Glass:
Science and Technology," vol. 5, Elasticity and Strength in
Glasses, Academic Press, Inc., May 28, 1980, pp. 145-216. cited by
applicant .
Gardon, Robert, "Tempering Glass with Modulated Cooling Schedules,"
Journal of the American Ceramic Society, vol. 71, No. 10, Oct.
1988, pp. 876-878. cited by applicant .
Gardon, Robert, "Variation of Densities and Refractive Indices in
Tempered Glass," Journal of the American Ceramic Society, vol. 61,
No. 3-4, Mar.-Apr. 1978, pp. 143-146. cited by applicant .
Glass, Jill et al., "Processing and Properties of Ion Exchanged
Glasses," Glass and Optical Materials Division Fall Meeting, Nov.
6-12, 2004, Cape Canaveral, FL, 33 slides. cited by applicant .
Glass, et al., "Stressed Glass Technology for Actuators and
Removable Barrier Applications," Sandia Report SAND2007-4106,
Sandia National Laboratories, Jul. 2007, 18 pages. cited by
applicant .
Gomez et al. "69-2: Designing Strong Glass for Mobile Devices," SID
Symposium Digest of Technical Papers, vol. 40, No. 1, Jan. 2009,
pp. 1045-1048NG Glass. cited by applicant .
Gross, TM., "Deformation and cracking behavior of glasses indented
with diamond tips of various sharpness," Journal of Non-Crystalline
Solids, vol. 358, Issue 24, Dec. 12, 2012, pp. 3445-3452. cited by
applicant .
Guillemet, C., "Annealing and Tempering of Glass," Journal of
Non-Crystalline Solids, vol. 123, 1990, pp. 415-426. cited by
applicant .
Gulati, Suresh T., "Frangibility ofTempered Soda-Lime Glass Sheet,"
Glass Processing Days, Sep. 13-15, 1997, pp. 72-76. cited by
applicant .
Gupta, Prabhat K. et al., "The laboratory glass transition," The
Journal of Chemical Physics, vol. 126, 2007, 9 pages. cited by
applicant .
Gupta, Prabhat, "Landscape Approach to Glass Transition and
Relaxation: Basic Concepts {contd.)," IMI-NFG's MITT Course on
Relaxation Processes in Glass Lecture 18, Mar. 25, 2010, 23 slides.
cited by applicant .
Gupta, Prabhat, "Landscape Approach to Glass Transition and
Relaxation: Four lectures on `The Landscape Approach,`" IMI-NFG's
MITT Course on Relaxation Processes in Glass Lecture 17, Mar. 23,
2010, 28 slides. cited by applicant .
Gupta, Prabhat, "Landscape Approach to Glass Transition and
Relaxation: Liquid to Glass Transition," IMI-NFG's MITT Course on
Relaxation Processes in Glass Lecture 19, Mar. 30, 2010, 25 slides.
cited by applicant .
Gupta, Prabhat, "Landscape Approach to Glass Transition and
Relaxation: Relaxation in the glassy state," IMI-NFG's Min Course
on Relaxation Processes in Glass Lecture 20, Apr. 1, 2010, 20
slides. cited by applicant .
Gy, Rene, "Ion exchange for glass strengthening," Materials Science
and Engineering B, vol. 149, 2008, pp. 159-165. cited by applicant
.
Hara, Morihisa et al., "Vickers Hardness of Toughened Sheet Glass,"
Reports of the Research Laboratory, Asahi Glass Co., Ltd., vol. 12,
No. 2, 1962, pp. 99-104. cited by applicant .
Hibino, Yoshinori et al., "Raman study on silica optical fibers
subjected to high tensile stress," Applied Physics Letters, vol.
47, No. 8, Oct. 15, 1985, pp. 812-814. cited by applicant .
Hodge, Ian M., "Physical Aging in Polymer Glasses," Science, vol.
267, No. 5206, Mar. 31, 1995, pp. 1945-1947. cited by applicant
.
Huang, Liping et al., "Polyamorphic transitions in vitreous 820 3
under pressure," Journal of Physics: Condensed Matter, vol. 20,
2008, 8 pages. cited by applicant .
Hubert, Mathieu, "Lecture 9: Annealing and tempering," IMI-NFG
Course on Processing in Glass--Lecture 9, Feb. 19, 2015, 72 slides.
cited by applicant .
Hutchins, J. and R. Harrington, "Glass", Kirk-Othmer Encyclopedia
of Chemical Technology, 2nd Edition, 10 pp. 533-604. cited by
applicant .
Ito, Setsuro, "Brittleness and Nano-Structure of Glass," 4th
International Workshop on Flow and Fracture of Advanced Glasses
Presentation, Nov. 5-7, 2007, Shiga, Japan, 37 slides. cited by
applicant .
Jain, Himanshu, "Electrical Relaxation--Topic 1: Quasi-free ion
transport," IMI-NFG's MITI Course on Relaxation Processes in Glass
Lecture 23, Advanced Vitreous State, The Properties of Glass:
Dielectric Properties--Lecture 1, 2010, 28 slides. cited by
applicant .
Jain, Himanshu, "Electrical Relaxation--Topic 2: Universal
dielectric response (UDR)," IMI-NFG's MITT Course on Relaxation
Processes in Glass Lecture 24, Advanced Vitreous State, The
Properties of Glass: Dielectric Properties--Lecture 1, 2010, 22
slides. cited by applicant .
Jain, Himanshu, "Electrical Relaxation--Topic 3: Nearly constant
loss--second universality," IMI-NFG's MITI Course on Relaxation
Processes in Glass Lecture 25, Advanced Vitreous State, The
Properties of Glass: Dielectric Properties--Lecture 3, 2010, 24
slides. cited by applicant .
Karlsson, Stefan et al., "The technology of chemical glass
strengthening--a review," Glass Technology, European Journal of
Glass Science Technology Part A, 51(2), Apr. 2010, pp. 41-54. cited
by applicant .
Kassir-Bodon, Assia et al., "Raman Mapping of the
Indentation-Induced Densification of a Soda-Lime-Silicate Glass,"
International Journal of Applied Glass Science, vol. 3, No. 1,
2012, pp. 29-35. cited by applicant .
Kiefer, Werner et al., "Method for Thermal Prestressing of Glass,"
Strength of Inorganic Glass, Plenum Press, New York, 1985, pp.
501-511. cited by applicant .
Kishii, Toru, "Surface Stress Meters Utilising the Optical
Waveguide Effect of Chemically Tempered Glasses," Optics and Lasers
in Engineering, vol. 4, 1983, pp. 25-38. cited by applicant .
International Search Report and Written Opinion PCT/US2016/044445
dated Oct. 14, 2016. cited by applicant .
International Search Report and Written Opinin PCT/US2016/044401
dated Jan. 2, 2017. cited by applicant .
International Search Report and Written Opinion PCT/US2016/044406
dated Nov. 25, 2016. cited by applicant .
Spaght, Monroe E_ et al., "Studies on Glass_ VIII. The Coefficient
of Thermal Expansion of Boron Trioxide," Journal of Physical
Chemistry, vol. 38, No. 1, 1934, pp. 103-110. cited by applicant
.
Specialty Glass Products, "Soda Lime/AR/Flint Glass";
http://www.sgpinc.com/sodalime.htm accessed Aug. 11, 2016. cited by
applicant .
Stillinger, Frank H., "A Topographic View of Supercooled Liquids
and Glass Formation," Science, New Series, vol. 267, No. 5206, Mar.
31, 1995, pp. 1935-1939. cited by applicant .
Stillinger, Frank H_ et al., "Packing Structures and Transitions in
Liquids and Solids," Science, New Series, vol. 225, No. 4666, Sep.
7, 1984, pp. 983-989. cited by applicant .
Tallant, D.R. et al., "The Effects of Tensile Stress on the Raman
Spectrum of the Silica Glass," Journal of Non-Crystalline Solids,
vol. 106, 1988, pp. 380-383. cited by applicant .
Tandon, Rajan et al., "Controlling the Fragmentation Behavior of
Stressed Glass," Fracture Mechanics of Ceramics, vol. 14, 2005, pp.
77. cited by applicant .
Tomlinson, R., G. Calvert, and A. Conway, A Photoelastic
Investigation Into Spontaneous Glass Fracture, Proceedings of the
XIth International Congress and Exposition, (Jun. 2008), 1st
sentence, p. 2--Book. cited by applicant .
Varughese, Binoy et al., "Effect of fictive temperature on
mechanical strength of soda-lime glasses," Journal of
Non-Crystalline Solids, vol. 241, 1998, pp. 134-139. cited by
applicant .
Walrafen, G_ E_ et al., "Raman investigation of optical fibers
under high tensile stress," Journal of Applied Physics, vol. 52,
No. 4, Apr. 1981, pp. 2832-2836. cited by applicant .
Wang, Fei et al., "Pressure Raman effects and internal stress in
network glasses," Physical Review B, vol. 71, 2005, 32 pages. cited
by applicant .
Weissmann, R and D. Durkop, "A Novel Method for Measuring Stresses
in Flat Glass", XV International Congress on Glass Leningrad 1898,
Proceeding 3b, O. V. Mazurin, ed., pp. 217-220. cited by applicant
.
Yamane, Masayuki, "Chapter 3: Thermal Processing," Glass
Engineering Handbook, Asakura Publishing Co_ Ltd., [8J Jul. 1999,
pp. 410-417. cited by applicant .
Yue, YL et al., "Determination of the fictive temperature for a
hyperquenched glass," Chemical Physics Letters, vol. 357, Issues
1-2, May 3, 2002, pp. 20-24. cited by applicant .
Zaman, F_ D_ et al., "Cooling of a Plate with General Boundary
Conditions," International Journal of Mathematics and Mathematical
Sciences, vol. 23, No. 7, 2000, pp. 477-485. cited by applicant
.
Aben, H. et al., "2.7 Stresses Due to Heterogeneities,"
Photoelasticity of Glass, Springer-Verlag, New York, 1993, 260
pages. cited by applicant .
Acloque, P., "Influence of Strain-Systems in Glass upon the Course
of its Fracture," Proceedings of the 4th International Glass
Congress, vol. 6, 1965, pp. 279-291. cited by applicant .
Acloque, Paul, "Comparison Between Heat-Transfer Conditions and
Setting Up of Strain in Glass During Heat-Treatment," Journal of
the American Ceramic Society, vol. 44, No. 7, Jul. 1961, pp.
364-373. cited by applicant .
Agarwal, Anand et al., "A simple IR spectroscopic method for
determining fictive temperature of silica glasses," Journal of
Non-Crystalline Solids, vol. 185, 1995, pp. 191-198. cited by
applicant .
Agarwal, Anand et al., "Determination of Fictive Temperature of
Soda-Lime Silicate Glass," Journal of the American Ceramic Society,
vol. 78, No. 3, Mar. 1995, pp. 827-829. cited by applicant .
Akeyoshi, K. et al., "Mechanical Properties of Tempered Glass,"
Proceedings of the 7th International Glass Congress, vol. 14, 1965,
pp. 80-85. cited by applicant .
Alexiades, V. et al., "The New Way/Glaston Problem," 28th Annual
Workshop on Mathematical Problems in Industry, University of
Delaware, Jun. 2012, 30 slides. cited by applicant .
Argon, A. S., "Chapter 3: Inelastic Deformation and Fracture in
Oxide, Metallic, and Polymeric Glasses," in, "Glass: Science and
Technology," vol. 5, Elasticity and Strength in Glass, Academic
Press, May 28, 1980, pp. 79-132. cited by applicant .
Aronen, Antti et al., "Tempering of Thin Glass," Glasstec 2012:
Engineered Transparency, Oct. 25-26, 2012, pp. 145-153. cited by
applicant .
Author Unknown, "Application Note AN 527: Depth profiling of
complex samples using confocal Raman microscopy," Bruker Optics
Inc., 2012, 3 pages. cited by applicant .
Author Unknown, "Architectural ERH2.TM.,"Architectural Glass
Systems, Glasstech, Inc., 2011, 2 pages. cited by applicant .
Author Unknown, "Architectural FCH2.TM.," Architectural Glass
Systems, Glasstech, Inc., 2011, 2 pages. cited by applicant .
Author Unknown, "Corning.RTM. Gorilla.TM. Glass," Corning
Incorporated, 2009, 2 pages. cited by applicant .
Author Unknown, "Glass Strengthening Methods," Abrisa Technologies,
Apr. 2015, 2 pages. cited by applicant .
Author Unknown, "Heat Treated Glass for Architectural Glazing,"
Glass Technical Document: TD-138, PPG Glass Technology, PPG
Industries, Inc., Nov. 2011, 8 pages. cited by applicant .
Author Unknown, "Introducing--Glasstech CRB-S.TM. 1900 for Solar
Parabolic Shapes," Solar Glass Systems, Glasstech, Inc., Date
Unknown, 1 page. cited by applicant .
Author Unknown, "New Way Air Bearings," 28th Annual Workshop on
Mathematical Problems in Industry, University of Delaware, Jun.
2012, 16 slides. cited by applicant .
Author Unknown, "Products, Glazing Techniques and Maintenance
Section 4: GGF Datasheet for the Quality of Thermally Toughened
Soda Lime Silicate Safety Glass for Building," Glass and Glazing
Federation, Aug. 2009, 12 pages. cited by applicant .
Author Unknown, "SCHOTT Technical Glasses--Physical and technical
properties," Schott North America, Inc., Feb. 2010, 44 pages. cited
by applicant .
Author Unknown, "scratch and dig numbers," Sizes, Inc., Last
Revised: Jun. 24, 2010, 5 pages,
http:/fwww.sizes.com/units/scratch_and_dig.htm. cited by applicant
.
Author Unknown, "Solar FCH-S.TM. ," Solar Glass Systems, Glasstech,
Inc., 2011, 2 pages. cited by applicant .
Author Unknown, "Standard Specification for Heat-Strengthened and
Fully Tempered Flat Glass," Designation: C 1048-12, ASTM
International Standard, 2015, 7 pages. cited by applicant .
Author Unknown, "Standard Specification for Heat-Treated Flat
Glass--Kind HS, Kind FT Coated and Uncoated Glass," Designation: C
1048-4, ASTM International Standard, 2009, 7 pages. cited by
applicant .
Author Unknown, "Subject Index," Date Unknown, pp. 277-282. cited
by applicant .
Author Unknown, "Tempered Glass," Tecnoglass,
www.tecnoglass.com/tempered.pdf, Date Unknown, 5 pages. cited by
applicant .
Author Unknown, "Thermal Tempering," EuropTec GmbH, Nov. 6, 2014, 2
pages. cited by applicant .
Author Unknown, "Unsteady Heat Transfer--HT3: Experimental Studies
of Thermal Diffusivities and Heat Transfer Coefficients", Date
Unknown, 27 slides. cited by applicant .
Ayinder, C.C. et al., "Thermal-Tempering Analysis of Bulk Metallic
Glass Plates Using an Instant-Freezing Model," Metallurgical and
Materials Transactions A, vol. 32A, Nov. 2001, pp. 2709-2715. cited
by applicant .
Baldwin, K. J. et al., "Confocal Raman Microspectroscopy through a
Planar Interface," Applied Spectroscopy, vol. 55, No. 5, 2001, pp.
517-524. cited by applicant .
Barr, J. W., "Glass Tempering by Numbers," Aug. 2008, 8 pages.
cited by applicant .
Barr, Jonathan W., "The Tempering Process," Cardinal Waxachachie
Tempering Seminar, Mar. 26, 2008, 36 slides. cited by applicant
.
Barr, Jonathan, "The Glass Tempering Handbook--Understanding the
Glass Tempering Process," Self Published, 2015, 52 pages,
http://www.lambertgtservices.co.uk/bookfTheGlassTemperingHandbook.pdf.
cited by applicant .
Barsom, John M., "Fracture of Tempered Glass," Journal of the
American Ceramic Society, vol. 51, No. 2, Feb. 1968, pp. 75-78.
cited by applicant .
Bartholomew, Roger F. et al., "Chapter 6: Chemical Strengthening of
Glass," in "Glass: Science and Technology," vol. 5, Elasticity and
Strength in Glass, Academic Press, May 28, 1980, pp. 217-270. cited
by applicant .
Beauchamp, Edwin K. et al., "Dynamics of Window Glass Fracture in
Explosions," Sandia Report SAND98-0598JC-700, Sandia National
Laboratories, May 1998, 74 pages. cited by applicant .
Bird, R. D., W. E. Stewart, and E. N. Lightfoot, Transport
Phenomena--Chapter 11: The Equations of Change for Nonisothermal
Systems, Wiley, (1960) pp. 349-373. cited by applicant .
Bird, R. D., W. E Stewart, and E. N. Lightfoot, Transport
Phenomena--Chapter 3: The Equations of Change for Isothermal
Systems, Wiley, (1960) pp. 75-113. cited by applicant .
Boaz, Prem, "Tempering Very Thin Glass--What Radio Waves Mean for
the Glass Industry," USGlass Magazine, vol. 45, Issue 3, Mar. 2010,
5 pages. cited by applicant .
Boaz, Prem, "Thin glass processing with radio wave assist," Glass
on Web, Last Reviewed: Jan. 2013, 6 pages, http://www.g lassonweb
.com/articles/article/561 /. cited by applicant .
Boguslavskii, I. A., "Studying the Nature of the Super-Strength of
Glasses Strengthened by the Thermophysical Method," Glass and
Ceramics, vol. 21, No. 10, Oct. 1964, pp. 562-567. cited by
applicant .
Brown, Angus M., "Nonlinear regression analysis of data using a
spreadsheet," Application Note, ISC, Oct. 2001, pp. 58-59. cited by
applicant .
Conradt, Reinhard, "I. Fragility and its Relation to other Glass
Properties," IMI-NFG's Min Course on Relaxation Processes in Glass
Lecture 21, Apr. 6-8, 2010, 61 slides. cited by applicant .
Conradt, Reinhard, "II. Networks," IIMI-NFG's Min Course on
Relaxation Processes in Glass Lecture 22, Apr. 6-8, 2010, 61
slides. cited by applicant .
Conway, Jr., Joseph C. et al., "Use of Crack Branching Data for
Measuring Near-Surface Residual Stresses in Tempered Glass,"
Journal of the American Ceramic Society, vol. 72, No. 9, Sep. 1989,
pp. 1584-1587. cited by applicant .
Cox, Dr. Chris, "Lecture 3: Complex exponential function, Fourier
and Laplace transforms," IMI-NFG's Min Course on Relaxation
Processes in Glass and Polymers Lecture 3, 2010, 25 slides. cited
by applicant .
Cox, Dr. Chris, "Lecture 4: Differential Equations," IMI-NFG's Min
Course on Relaxation Processes in Glass and Polymers Lecture 4,
2010, 24 slides. cited by applicant .
Danish Kin, G. K. et al., "Development of a Continuous Method of
Bending and Toughening Glass," Glass and Ceramics, vol. 34, Issue
8, Aug. 1977, pp. 495-498. cited by applicant .
Daudeville, L. et al., "Numerical Simulation of Soda-Lime Silicate
Glass Tempering," Journal de Physique IV, France, vol. 6, No. C1,
Jan. 1996, pp. C1-175-C1-185. cited by applicant .
Daudeville, Laurent et al., "Thermal Tempering Simulation of Glass
Plates: Inner and Edge Residual Stresses," Journal of Thermal
Stresses, vol. 21, 1998, pp. 667-689. cited by applicant .
De Grauw, C. J. et al., "Axial resolution of confocal Raman
microscopes: Gaussian beam theory and practice," Journal of
Microscopy, vol. 188, Pt. 3, Dec. 1997, pp. 273-279. cited by
applicant .
Bandyopadhyay et al; "Application of Fused Deposition in Controlled
Microstructure Metal-Ceramic Composites" , Rapid Prototyping
Journal, vol. 12 Issue 3, pp. 121 128 (2006. cited by applicant
.
Wang et al; "Glass and Hot Extrusion by Me Module for 3D Additive
Manufacturing" ; IEEE, 2016; pp. 1167-1171. cited by applicant
.
Narayanaswamy, O. S., "Stress and Structural Relaxation in
Tempering Glass" , Journal of the American Ceramic Society, vol.
61, No. 3-4, (Mar. 4, 1978), pp. 146-152. cited by applicant .
Klein et al; "Additive Manufacturing of Optically Transparent
Glass" ; 3D Printing and Additive Manufacturing; vol. 2, No. 3;
2015; pp. 92-105. cited by applicant .
Luo et al; "Additive Manufacturing of Glass for Optical
Applications"; Proc. of SPIE, vol. 9738, 2016; pp.
97380Y-1-97380Y-9. cited by applicant .
Kistler, S_ S., "Stresses in Glass Produced by Nonuniform Exchange
of Monovalent Ions," Journal of the American Ceramic Society, vol.
45, No. 2, Feb. 1962, pp. 59-68. cited by applicant .
Koike, A. et al, "Fictive temperature dependence of subcritical
crack growth rate of normal glass and anomalous glass," Journal of
Non-Crystalline Solids, vol. 352, 2006, pp. 5522-5530. cited by
applicant .
Kong et al; "Residual Stress Analysis With Improved Numerical
Methods for Tempered Plate Glasses Based on Structural Relaxation
Model"; Metals and Materials International, vol. 13, No. 1 (2007);
pp. 67-75. cited by applicant .
Lathabai, Srinivasarao et al., "Fracture mechanics model for
subthreshold indentation flaws: Part 1--Equilibrium fracture,"
Journal of Materials Science, vol. 26, 1991, pp. 2157-2168. cited
by applicant .
Lee et al., "Glass Thickness and Fragmentation Behavior in Stressed
Glasses," New Journal of Glass and Ceramics, vol. 2, 2012, pp.
138-143. cited by applicant .
Lezzi et al., "Confirmation of Thin Surface Residual Compressive
Stress in Silica Glass Fiber by FTIR Reflection Spectroscopy,"
Journal of Non-Crystalline Solids, vol. 390, 2014, pp. 13-18. cited
by applicant .
Li et al., "Effect of Fictive Temperature on Dynamic Fatigue
Behavior of Silica and Soda-Lime Glasses," Journal of the American
Ceramic Society, vol. 78, No. 5, 1995, pp. 1393-1396. cited by
applicant .
Loucks, "Lecture 13: The Fictive and Glass Transition
Temperatures," IMI-NFG's Min Course on Relaxation Processes in
Glass Lecture 13, Mar. 2, 2010, 25 Slides. cited by applicant .
Loucks, "Lecture 14: Relaxation and the Tool-Narayanaswamy-Moynihan
Equation," IMI-NFG's MITT Course on Relaxation Processes in Glass
Lecture 14, Mar. 4, 2010, 27 Slides. cited by applicant .
Loucks, "Lecture 15: The Tool-Narayanaswamy-Moynihan Equation Part
II and DSC," IMI-NFG's MITT Course on Relaxation Processes in Glass
Lecture 15, Mar. 9, 2010, 33 Slides. cited by applicant .
Loucks, "Lecture 16: The Tool-Narayanaswamy-Moynihan Equation Part
II and DSC," IMI-NFG's MITT Course on Relaxation Processes in Glass
Lecture 16, Mar. 11, 2010, 32 Slides. cited by applicant .
Markovsky, et al., "An Efficient and Stable Algorithm for
Calculating Fictive Temperatures," Communications of the American
Ceramic Society, Apr. 1984, 2 Pages. cited by applicant .
Martin, "Lecture 10: Thermodynamic Functions," IMI-NFG's Min Course
on Relaxation Processes in Glass Lecture 10, 2010, 25 Slides. cited
by applicant .
Martin, Dr Steve, "Lecture 11: Thermodynamics in the Glass
Transition Region," IMI-NFG's MITT Course on Relaxation Processes
in Glass Lecture 11, 2010, 22 slides. cited by applicant .
Martin, Dr. Steve, "Lecture 12: The Glass Transition as a Kinetic
Transition," IMI-NFG's MITT Course on Relaxation Processes in Glass
Lecture 12, 2010, 21 slides. cited by applicant .
Martin, Dr. Steve, "Lecture 9: Thermodynamic Concepts and the Law
of Thermodynamics," IMI-NFG's MITT Course on Relaxation Processes
in Glass Lecture 9, 2010, 32 slides. cited by applicant .
Mass En, Claire P. et al., "Power-law distributions for the areas
of the basins of attraction on a potential energy landscape,"
Physical Review E, The American Physical Society, vol. 75, 2007, 4
pages. cited by applicant .
Mauricio-Iglesias, M. et al., "Raman depth-profiling
characterization of a migrant diffusion in a polymer," Journal of
Membrane Science, vol. 375, 2011, pp. 165-171. cited by applicant
.
McGlinchy, Timothy B., "Energy Efficient Tripe IG Automation EEE
(Triple-E)," DE-EE0000167, GED Integrated Solutions, Feb. 28, 2013,
45 pages=. cited by applicant .
McMaster, Ronald A., "Flat Glass Tempering--How It Works," Glass
Industry, Jun. 1989, pp. 10-15. cited by applicant .
McMaster, Ronald A., "Fundamentals of Tempered Glass," Proceedings
of the 49th Conference on Glass Problems: Ceramic Engineering and
Science Proceedings, vol. 10, Issue 3/4, 1989, pp. 193-206. cited
by applicant .
McMaster, Ronald A_ et al., "Annealed and Tempered Glass,"
Engineered Materials Handbook, vol. 4, Ceramics and Glasses, 1991,
9 pages. cited by applicant .
Mikowski, A. et al., "Statistical analysis of threshold load for
radial crack nucleation by Vickers indentation in commercial
soda-lime silica glass," Journal of Non-Crystalline Solids, vol.
352, 2006, pp. 3544-3549. cited by applicant .
Mognato, Ennio et al., "Thermally toughened safety glass," Glass on
Web, Last Reviewed: Jul. 2011, 9 pages,
http://www.glassonweb.com/articles/article/727/. cited by applicant
.
Moynihan, c_ T. et al., "Structural Relaxation in Vitreous
Materials," Annals of the New York Academic of Sciences, vol. 279,
Oct. 1976, pp. 15-35. cited by applicant .
Narayanaswamy, 0. S. et al., "Calculation of Residual Stresses in
Glass," Journal of the American Ceramic Society, vol. 52, No. 10,
Oct. 1969, pp. 554-558. cited by applicant .
Narayanaswamy, 0. S., "Stress and Structural Relaxation in
Tempering Glass," Journal of the American Ceramic Society, vol. 61,
No. 3-4, Mar.-Apr. 1978, pp. 146-152. cited by applicant .
Oakley, David R., "Crack branching in float glass subjected to
biaxial loading," Journal of Non-Crystalline Solids, vol. 196,
1996, pp. 139-143. cited by applicant .
"Ohlberg et al.," "Thermal Stress Calculations Based on a Linear
Viscoelastic Deviatoric Response and a Fictive Temperature
Component for the Volumetric Response," "Journal of Non-Crystalline
Solids, vol. 14, 1974, pp. D280-D286". cited by applicant .
Paschel, Richard, "History of the Safety Glazing Certification
Council," Safety Glazing Certification Council, Date Unknown, 11
pages. cited by applicant .
Ray, N. H. et al., "Increasing the strength of glass by treatment
in molten salts," Physics and Chemistry of Glasses, vol. 8, No. 1,
Feb. 1967, pp. 30-34. cited by applicant .
Rekhson, S. M., "Chapter 1: Viscoelasticity of Glass," in "Glass:
Science and Technology," vol. 3, 1986, 117 pages. cited by
applicant .
Rekson, S. M., "Structural Relaxation and Shear Stresses in the
Glass-Transition Region," Soviet Journal of Glass Physics and
Chemistry, 1975, pp. 417-421. cited by applicant .
Sastry, Srikanth, "The relationship between fragility,
configurational entropy and the potential energy landscape of
glass-forming liquids," Nature, vol. 409, Jan. 11, 2001, pp.
164-167. cited by applicant .
Scherer, George W., "Use of the Adam-Gibbs Equation in the Analysis
of Structural Relaxation," Journal of the American Ceramic Society,
vol. 67, No. 7, Jul. 1984, pp. 504-511. cited by applicant .
Sciortino, Francesco, "Potential energy landscape description of
supercooled liquids and glasses," Journal of Statistical Mechanics:
Theory and Experiment, May 31, 2005, 35 pages. cited by applicant
.
Sehgal, Jeetendra et al., "A New Low-Brittleness Glass in the
Soda-Lime-Silica Glass Family," Journal of the American Ceramic
Society, vol. 81, No. 9, Sep. 1998, pp. 2485-2488. cited by
applicant .
Setsuro, Ito et al., "Processing Technical Books to the Glass
High-Functions," Chapter 3: Sections 2.5, 3, 3.1, 3-2, [8J &
3.3, Science & Technology Co., Ltd., Sep. 27, 2012, pp. 58-65.
cited by applicant .
Sglavo, V., A. Prezzi, M. Alessandrini, "Processing of Glasses with
Engineered Stress Profiles," Journal of Non-Crystalline Solids, 344
(2004), 73-78. cited by applicant .
Shelby "Introduction to Glass Science and Technology"; The Royal
Chemical Society; 2nd Edition, 2005; p. 193. cited by applicant
.
Shimodaira, N_ et al., "Raman spectra of fluorine-doped silica
glasses with various fictive temperatures," Journal of Applied
Physics, vol. 91, No. 6, Mar. 15, 2002, pp. 3522-3525. cited by
applicant .
Shin Kai, Norihiko et al., "Indentation Fracture of Tempered
Glasses," Reports of the Research Laboratory, Asahi Glass Co.,
Ltd., vol. 23, No. 2, 1973, pp. 83-99. cited by applicant .
Shouyuan, Zhai et al., "Influence of Temperature and Time on Glass
Strength During Chemical Tempering," [8J Journal of Shangdong
Institute of Light Industry (Natural Science Edition), Feb. 1996, 3
pages. cited by applicant .
Shutov, A_ I. et al., "Prediction of the Character of Tempered
Glass Fracture," Glass and Ceramics, vol. 55, Nos. 1-2, 1998, pp.
8-10. cited by applicant .
Soules, Thomas F_ et al., "Finite-Element Calculation of Stresses
in Glass Parts Undergoing Viscous Relaxation," Journal of the
American Ceramic Society, vol. 70, No. 2, Feb. 1987, pp. 90-95.
cited by applicant .
Southard, J_ C., "The Thermal Properties of Crystalline and Glassy
Boron Trioxide," Journal of the American Chemical Society, vol. 63,
No. 11, Nov. 1941, pp. 3147-3150. cited by applicant .
International Search Report and Written Opinion PCT/US2015/042955
dated Nov. 4, 2015. cited by applicant .
International Search Report and Written Opinion PCT/US2016/045022
dated Jan. 31, 2017. cited by applicant .
International Searching Authority Invitation to Pay Additional Fees
PCT/US2016/045022 dated Oct. 28, 2016. cited by applicant .
International Search Report and Written Opinion PCT/US2015/042965
dated Nov. 2, 2015. cited by applicant .
Author Unknown, "Introducing--Glasstech CRB-S.TM. 1900 for Solar
Parabolic Shapes," Solar Glass Systems, Glasstech, Inc., Date
Unknown, 1 page, Retrieved Jul. 1, 2015. cited by applicant .
Author Unknown, "Subject Index," Date Unknown, pp. 277-282,
Retrieved Apr. 24, 2015. cited by applicant .
Author Unknown, "Tempered Glass," Tecnoglass,
www.tecnoglass.com/tempered.pdf, Date Unknown, 5 pages, Retrieved
Jul. 28, 2015. cited by applicant .
Author Unknown, "Unsteady Heat Transfer--HT3: Experimental Studies
of Thermal Diffusivities and Heat Transfer Coefficients," Date
Unknown, 27 slides, Retrieved Jul. 21, 2015. cited by applicant
.
Electronic Cooling Editors, "The Thermal Conductivity of Gases",
Design, Materials, Adhesives, Substrates, No. 3, Technical Data,
Test & Measurement, vol. 4, Gases, Thermal Conductivity, Sep.
1, 1998, 2 pages. cited by applicant .
Hutchins, J. and R. Harrington, "Glass", Kirk-Othmer Encyclopedia
of Chemical Technology, 2nd Edition, 10 pp. 533-604, Retrieved Jan.
9, 2017. cited by applicant .
Paschel, Richard, "History of the Safety Glazing Certification
Council," Safety Glazing Certification Council, Date Unknown, 11
pages, Retrieved Jul. 21, 2015. cited by applicant.
|
Primary Examiner: Sample; David
Attorney, Agent or Firm: Magaziner; Russell S.
Parent Case Text
This is a national stage application under 35 U.S.C. .sctn. 371 of
International Application No. PCT/US2016/044406, filed on Jul. 28,
2016, which claims benefit of priority to U.S. Provisional
Application Ser. No. 62/236,296 filed on Oct. 2, 2015 and U.S.
Provisional Application Ser. No. 62/288,851 filed on Jan. 29, 2016
and U.S. Provisional Application Ser. No. 62/286,192 filed on Jan.
22, 2016 and claims the benefit of priority under 35 U.S.C. .sctn.
120 of U.S. application Ser. No. 14/814,232 filed on Jul. 30, 2015
and U.S. application Ser. No. 14/814,274 filed on Jul. 30, 2015 and
U.S. application Ser. No. 14/814,293 filed on Jul. 30, 2015 and
U.S. application Ser. No. 14/814,303 filed on Jul. 30, 2015 and
U.S. application Ser. No. 14/814,363 filed on Jul. 30, 2015 and
U.S. application Ser. No. 14/814,319 filed on Jul. 30, 2015 and
U.S. application Ser. No. 14/814,335 filed on Jul. 30, 2015 the
entire contents of which are relied upon and incorporated herein by
reference in its entirety.
Claims
What is claimed is:
1. A consumer electronic product comprising: an electronic display
comprising a front surface, a back surface, and at least one side
surface; a glass-based layer comprising a first major surface
opposite a second major surface with an interior region located
therebetween; wherein the glass-based layer is provided at least
partially over the electronic display; wherein an average thickness
between the first and second major surfaces of the glass-based
layer is less than 2 mm; wherein an ion content and chemical
constituency of at least a portion of both the first major surface
and the second major surface of the glass-based layer is the same
as an ion content and chemical constituency of at least a portion
of the interior region of the glass-based layer; wherein the first
and second major surfaces of the glass-based layer are under
compressive stress greater than 150 MPa and the interior region of
the glass-based layer is under tensile stress; wherein a surface
roughness of the first major surface of the glass-based layer is
between 0.2 and 1.5 nm Ra roughness.
2. The consumer electronic product of claim 1, wherein the stress
within the glass-based layer varies as a function of position
relative to the first and second major surfaces, wherein the stress
within the glass-based layer has a change of at least 200 MPa over
a distance of less than 500 .mu.m of the thickness of the
glass-based layer.
3. The consumer electronic product of claim 1, wherein a surface
roughness of the second major surface of the glass-based layer is
between 0.2 and 1.5 nm Ra roughness.
4. The consumer electronic product according to claim 1, wherein
the first and second major surfaces of the glass-based layer are
flat to at least 50 .mu.m total indicator run-out along a 50 mm
profile of the first and second major surfaces.
5. The consumer electronic product according to claim 1, wherein
the areas of the first and second major surfaces of the glass-based
layer are at least 2500 mm.sup.2.
6. The consumer electronic product according to claim 1, wherein
the glass-based layer further comprises a surface feature on the
first or second major surface for haptic feedback.
7. The consumer electronic product according to claim 1, wherein
the average thickness of the glass-based layer is about 0.1 mm to
about 1.5 mm.
8. The consumer electronic product according to claim 1, wherein
the glass-based layer further comprises a depth of compression
>17% of the distance between the first and second major
surfaces.
9. The consumer electronic product according to claim 1, wherein
the glass-based layer is soda-lime glass, alkali aluminosilicate
glass, alkali containing borosilicate glass, alkali
aluminophosphosilicate glass, or alkali aluminoborosilicate
glass.
10. The consumer electronic product according to claim 1, wherein
the first or second major surface of the glass-based layer further
comprises at least one of an anti-scratch layer, an antireflection
layer, and an antiglare layer.
11. The consumer electronic product according to claim 1, wherein
the electronic display is a touch-sensitive display.
12. The consumer electronic product according to claim 1, wherein
the electronic display is a liquid crystal display (LCD).
13. The consumer electronic product according to claim 1, wherein
the electronic display includes at least one light emitting diode
(LED).
14. The consumer electronic product according to claim 1, wherein
the glass-based layer extends across the housing front surface from
the at least one side surface to an opposite side surface.
15. The consumer electronic product according to claim 1, wherein
the product is a mobile phone, a portable media player, a
television, a notebook computer, a watch, a household appliance, or
a tablet computer.
16. A consumer electronic product comprising: a housing having a
front surface, a back surface, and at least one side surface;
electrical components provided at least partially internal to the
housing, the electrical components comprise at least a controller,
a memory, and a display; the back surface comprising a glass-based
layer comprising a first major surface opposite a second major
surface with an interior region located therebetween; wherein an
average thickness between the first and second major surfaces of
the glass-based layer is less than 2 mm; wherein an ion content and
chemical constituency of at least a portion of both the first major
surface and the second major surface of the glass-based layer is
the same as an ion content and chemical constituency of at least a
portion of the interior region of the glass-based layer wherein the
first and second major surfaces of the cover glass are under
compressive stress greater than 150 MPa and the interior region of
the cover glass is under tensile stress; wherein a surface
roughness of the first major surface of the cover glass is between
0.2 and 1.5 nm Ra roughness.
17. The consumer electronic product of claim 16, wherein the glass
based layer is a glass or glass-ceramic material.
18. The consumer electronic product of claim 16, wherein the
glass-based layer further comprises a surface feature on the first
or second major surface for haptic feedback.
Description
BACKGROUND
The disclosure relates generally to thermally conditioned (e.g.,
strengthened, tempered, heated, etc.) cover glass for consumer
electronic applications, and specifically relates to thermally
strengthened glass and to related methods and systems for the
thermal strengthening of glass for consumer electronic
applications, particularly for thin consumer electronic glass
sheets (also called "cover glass" herein).
In thermal (or "physical") strengthening of glass sheets, a glass
sheet is heated to an elevated temperature above the glass
transition temperature of the glass and then the surfaces of the
sheet are rapidly cooled ("quenched") while the inner regions of
the sheet cool at a slower rate. The inner regions cool more slowly
because they are insulated by the thickness and the fairly low
thermal conductivity of the glass. The differential cooling
produces a residual compressive stress in the glass surface
regions, balanced by a residual tensile stress in the central
regions of the glass.
Thermal strengthening of glass is distinguished from chemical
strengthening of glass, in which surface compressive stresses are
generated by changing the chemical composition of the glass in
regions near the surface by a process such as ion diffusion. In
some ion diffusion based processes, exterior portions of glass may
be strengthened by exchanging larger ions for smaller ions near the
glass surface to impart a compressive stress (also called negative
tensile stress) on or near the surface. The compressive stress is
believed to limit crack initiation and/or propagation.
Thermal strengthening of glass also is distinguished from glass
strengthened by processes in which exterior portions of the glass
are strengthened or arranged by combining two types of glass. In
such processes, layers of glass compositions that have differing
coefficients of thermal expansion are combined or laminated
together while hot. For example, by sandwiching molten glass with a
higher coefficient of thermal expansion (CTE) between layers of
molten glass with a lower CTE, positive tension in the interior
glass compresses the outer layers when the glasses cool, again
forming compressive stress on the surface to balance the positive
tensile stress. This surface compressive stress provides
strengthening.
Thermally strengthened consumer electronic glass or cover glass has
advantages relative to unstrengthened glass. The surface
compression of the strengthened consumer electronic glass or cover
glass provides greater resistance to fracture than unstrengthened
glass. The increase in strength generally is proportional to the
amount of surface compression stress. If a sheet possesses a
sufficient level of thermal strengthening, relative to its
thickness, then if the sheet is broken, generally it will divide
into small fragments rather than into large or elongated fragments
with sharp edges. Glass that breaks into sufficiently small
fragments, or "dices," as defined by various established standards,
may be known as safety glass, or "fully tempered" glass, or
sometimes simply "tempered" glass.
Because the degree of strengthening depends on the temperature
difference between the surface and center of the glass sheet during
quenching, thinner glasses require higher cooling rates to achieve
a given stress. Also, thinner glass generally requires higher
values of surface compressive stress and central tension stress to
achieve dicing into small particles upon breaking. Accordingly,
achieving desirable levels of tempering in glass with thicknesses
of around 3 mm or less has been exceedingly challenging, if not
impossible.
Aspects of the present disclosure also relate to consumer
electronic glass or cover glass that has a stress profile for
strengthening exterior portions thereof. Consumer electronic glass,
such as cover glass for use on any surface of a consumer electronic
device, may be used for a broad range of applications Such
applications include cell phones, tablets, mobile phones, personal
computers, notebook computers, digital signage, digital white
board, etc.
Aspects of the present disclosure also relate generally to glass or
glass-ceramic that has a stress profile for strengthening exterior
portions thereof. Glass and glass-ceramic articles, such as sheets
of glass, may be used for a broad range of applications. Examples
of such applications include use in windows, countertops,
containers (e.g., food, chemical), use as a backplane, frontplane,
cover glass, etc., for a display device (e.g., tablet, cellular
phone, television), use as a high-temperature substrate or support
structure, or other applications.
SUMMARY
This disclosure relates, in part, to highly strengthened thin
consumer electronic glass or cover glass sheets and articles, and
to methods, processes, and systems that achieve surprisingly high
levels of heat strengthening of consumer electronic glass or cover
glass sheets at thicknesses not achieved in the past. In various
embodiments, the process and method of the current disclosure is
believed to surpass the consumer electronic glass or cover glass
thickness limits and heat transfer rates provided by conventional
convective gas thermal strengthening processes without the need to
contact the consumer electronic glass or cover glass with liquid or
solid heat sinks. In such systems and processes, during quenching,
the cover glass is contacted only with a gas. The systems and
methods disclosed enable thermal strengthening, including up to
"full temper" or dicing behavior, in cover glass sheets having
thicknesses down to at least as thin as 0.1 mm (in at least some
contemplated embodiments); and in some embodiments, provides this
strengthening in a thin cover glass sheet that also has a low
roughness and a high degree of flatness resulting from the lack of
liquid or solid contact during quenching. In various embodiments,
these advantageous cover glass sheet material properties are
provided by a system and method with substantially lower quenching
power requirements, as compared to conventional convective glass
tempering systems.
One embodiment of the disclosure relates to a process for thermally
strengthening a consumer electronic glass or cover glass material.
The process includes providing article formed from a glass
material. The process includes heating the article above a glass
transition temperature of the cover glass material. The process
includes moving the heated article into a cooling station. The
cooling station includes a heat sink having a heat sink surface
facing the heated article and a gas gap separating the heat sink
surface from the heated article such that the heat sink surface
does not touch the heated article. The process includes cooling the
heated article to a temperature below the cover glass transition
temperature such that surface compressive stresses and central
tensile stresses are created within the article. The article is
cooled by transferring thermal energy from the heated article to
the heat sink by conduction across the gap such that more than 20%
of the thermal energy leaving the heated article crosses the gap
and is received by the heat sink.
Another embodiment of the disclosure relates to a system for
thermally strengthening a cover glass sheet. The system includes a
heating station including a heating element delivering heat to the
cover glass sheet, and the cover glass sheet includes a first major
surface, a second major surface and a thickness between the first
and second major surfaces. The system includes a cooling station,
including opposing first and second heat sink surfaces defining a
channel therebetween such that during cooling the cover glass sheet
is located within the channel. The system includes a gas bearing
delivering pressurized gas to the channel such that the cover glass
sheet is supported within the channel without touching the first
and second heat sink surfaces, and the gas bearing defines a gap
area. The gas bearing delivers a gas into the channel such that a
total mass flow rate of gas into the channel is greater than zero
and less than 2k/gC.sub.p per square meter of gap area, where k is
the thermal conductivity of a gas within the channel evaluated in
the direction of heat conduction, g is the distance between the
cover glass sheet and the heat sink surface, and C.sub.p is the
specific heat capacity of the gas within the channel.
Another embodiment of the disclosure relates to a strengthened
consumer electronic glass/cover glass or glass-ceramic article. The
article includes a first major surface, a second major surface
opposite the first major surface and an interior region located
between the first and second major surfaces. The article includes
an average thickness between the first major surface and second
major surface of less than 2 mm. The article includes at least 70%
silicon dioxide by weight. An ion content and chemical constituency
of at least a portion of both the first major surface and the
second major surface is the same as an ion content and chemical
constituency of at least a portion of the interior region. The
first major surface and the second major surfaces are under
compressive stress and the interior region is under tensile stress,
and the compressive stress is greater than 150 MPa. A surface
roughness of the first major surface is between 0.2 and 2.0 nm
R.sub.a roughness.
Another embodiment of the disclosure relates to a strengthened
consumer electronic glass or cover glass on a consumer electronic
product. In embodiments, the consumer electronic product includes
an electronic display with a front surface, a back surface, and at
least one side surface. In embodiments, a glass-based layer or
cover glass is provided at least partially over the electronic
display. In embodiments, the glass-based layer or cover glass
includes a first major surface opposite a second major surface with
an interior region located therebetween. In embodiments, the
glass-based layer or cover glass includes an average thickness
between the first major surface and second major surface of less
than 2 mm. In embodiments, an ion content and chemical constituency
of at least a portion of both the first major surface and the
second major surface is the same as an ion content and chemical
constituency of at least a portion of the interior region. In
embodiments, the first major surface and the second major surfaces
are under compressive stress and the interior region is under
tensile stress, and the compressive stress is greater than 150 MPa.
In embodiments, a surface roughness of the first major surface is
between 0.2 and 2.0 nm R.sub.a roughness.
Another embodiment of the disclosure relates to a strengthened
consumer electronic glass or cover glass for a consumer electronic
product. In embodiments, the consumer electronic product includes a
housing with a front surface, a back surface, and at least one side
surface. In embodiments, electrical components, including at least
a controller, a memory, and a display, are provided at least
partially internal to the housing. In embodiments, a glass-based
layer or back glass is provided on or over the back surface of the
housing. In embodiments, the glass-based layer or back glass
includes a first major surface opposite a second major surface with
an interior region located therebetween. In embodiments, the
glass-based layer or back glass includes an average thickness
between the first major surface and second major surface of less
than 2 mm. In embodiments, an ion content and chemical constituency
of at least a portion of both the first major surface and the
second major surface is the same as an ion content and chemical
constituency of at least a portion of the interior region. In
embodiments, the first major surface and the second major surfaces
are under compressive stress and the interior region is under
tensile stress, and the compressive stress is greater than 150 MPa.
In embodiments, a surface roughness of the first major surface is
between 0.2 and 2.0 nm R.sub.a roughness.
Another embodiment of the present disclosure relates to a consumer
electronic product including a strengthened consumer electronic
glass or cover glass. In embodiments, the consumer electronic
product includes a housing with a front surface, a back surface,
and at least one side surface. In embodiments, electrical
components are provided at least partially internal to the housing.
In embodiments, the electrical components include at least a
display. In embodiments, the consumer electronic glass or cover
glass is provided as or adjacent the front surface of the housing.
In embodiments, the glass based layer or cover glass includes a
first major surface and a second major surface separated by the
thickness. In embodiments, the first major surface of the
glass-based layer or cover glass is flat to 100 .mu.m total
indicator run-out (TIR) along any 50 mm or less profile of the
first major surface of the glass-based layer or cover glass. In
embodiments, the glass-based layer or cover glass includes a glass
material having a low temperature linear CTE, expressed in
1/.degree. C., of .alpha..sup.S.sub.CTE, a high temperature linear
CTE, expressed in 1/.degree. C., of .alpha..sup.L.sub.CTE, an
elastic modulus, expressed in GPa, of E, a strain temperature,
expressed in units of .degree. C., of T.sub.strain, and a softening
temperature, expressed in units of .degree. C., of T.sub.soft. In
further embodiments, the first major surface of the second
glass-based layer has a thermally induced surface compressive
stress of less than 600 MPa and greater than
.function..function..alpha..alpha. ##EQU00001## in units of MPa;
wherein P.sub.1 is given by
##EQU00002## P.sub.2 is given by
##EQU00003## and h is greater than or equal to 0.020
cal/scm.sup.2.degree. C.
Yet another embodiment of the present disclosure relates to a
consumer electronic product including a strengthened consumer
electronic glass or cover glass. In embodiments, the consumer
electronic product includes a housing with a front surface, a back
surface, and at least one side surface. In embodiments, electrical
components, including at least a controller, a memory, and a
display, are provided at least partially internal to the housing.
In embodiments, a glass-based layer or cover glass is provided at
or adjacent the front surface of the housing. In embodiments, the
glass-based layer or cover glass is provided at least partially
over the display. In embodiments, the glass-based layer or cover
glass includes a first major surface opposite a second major
surface with an interior region located therebetween. In
embodiments, the first major surface is flat to 100 .mu.m total
indicator run-out (TIR) along any 50 mm or less profile of the
first major surface. In embodiments, the glass-based layer cover
glass includes a glass material having a softening temperature,
expressed in units of .degree. C., of T.sub.soft and an annealing
temperature, expressed in units of .degree. C., of T.sub.anneal,
and a surface fictive temperature measured on the first major
surface represented by Tfs, when expressed in units of .degree. C.
In embodiments, the glass-based layer or cover glass having a
non-dimensional surface fictive temperature parameter .theta.s
given by (Tfs-T.sub.anneal)/(T.sub.soft-T.sub.anneal). In
embodiments, the parameter .theta.s is in the range of from 0.20 to
0.9.
Additional features and advantages will be set forth in the
detailed description that follows, and, in part, will be readily
apparent to those skilled in the art from the description or
recognized by practicing the embodiments as described in the
written description and claims hereof, as well as the appended
drawings.
It is to be understood that both the foregoing general description
and the following detailed description are merely exemplary, and
are intended to provide an overview or framework to understand the
nature and character of the claims.
The accompanying drawings are included to provide a further
understanding and are incorporated in and constitute a part of this
specification. The drawings illustrate one or more embodiments, and
together with the description serve to explain principles and the
operation of the various embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 (Prior Art) is a graph of blower power required for "full
tempering" as a function of glass thickness.
FIG. 2 (Prior Art) is a graph of blower power required for "full
tempering" as a function of glass thickness for an old process or
machine O and a newer process or machine N.
FIG. 3 (Prior Art) is a graph of the old curve O and the new curve
N of FIG. 2 scaled to match and superimposed upon the graph of FIG.
1.
FIG. 4 is a perspective view of a consumer electronic/cover glass
or glass-ceramic article or sheet according to an exemplary
embodiment.
FIG. 5 is a diagrammatic partial cross-section of a thermally
strengthened consumer electronic glass sheet or cover glass of FIG.
4 according an exemplary embodiment.
FIG. 6 is a graphical representation of estimated tensile stress
versus thickness for a glass or glass-ceramic article according to
an exemplary embodiment.
FIG. 7 shows a portion of a fractured cover glass or glass-ceramic
article according to an exemplary embodiment.
FIG. 8 is a plot of fragmentation per square centimeter as a
function of positive tensile stress from experiment.
FIG. 9 is a plot of the magnitude of negative tensile stress at the
surface as a function of initial hot zone temperature from
experiment, showing a threshold to achieve dicing.
FIG. 10 is a plot of the non-dimensional surface fictive
temperature parameter .theta.s for fictive temperatures obtained by
one or more embodiments of methods and systems of the present
invention.
FIG. 11 is a plot of surface compression stresses calculated by
simulation for differing glass compositions, plotted against a
proposed temperability parameter .PSI. for the various compositions
shown.
FIGS. 12 and 13 are graphs of two parameters P.sub.1 and P.sub.2 as
functions of heat transfer coefficient h.
FIG. 14 is a graph of MPa of surface compression of a glass sheet
as a function of thickness t of the sheet in millimeters, showing
regions of performance newly opened by one or more embodiments of
the systems and methods of the present disclosure.
FIG. 15 is a graph showing compressive stress as a function of
thickness plotted for selected exemplary embodiments of tempered
glass sheets of the present disclosure.
FIG. 16 is a flow chart illustrating some aspects of a method
according to the present disclosure.
FIG. 17 is a flow chart illustrating some aspects of another method
according to the present disclosure.
FIG. 18 is the graph of FIG. 3 with a region R and points A, B, A'
and B' marked thereon to show a region in which the methods and
systems of the present disclosure allow operation, in contrast to
the prior art.
FIG. 19 is another representation of the region R and points A, B,
A' and B' of FIG. 18, but shown adjacent to (and positioned
relative to the scale) of a reduced size copy of FIG. 2.
FIG. 20 (Prior Art) is a graph of the required heat transfer
coefficient needed for tempering as a function of glass
thickness.
FIG. 21 is a diagrammatic cross-section of a glass sheet being
cooled by conduction more than by convection, according to an
exemplary embodiment.
FIG. 22 is a schematic cross-sectional diagram of a conductive
strengthening system according to an exemplary embodiment.
FIG. 23 is a perspective cut-away view of another embodiment of a
system similar to that of FIG. 22 according to an exemplary
embodiment.
FIG. 24 is a perspective cut-away view of an alternative embodiment
of the inset feature of FIG. 23 according to an exemplary
embodiment.
FIG. 25 is a perspective cut-away view of yet another alternative
embodiment of the inset feature of FIG. 23 according to an
exemplary embodiment.
FIG. 26 is a flow chart illustrating some aspects of yet another
method according to an exemplary embodiment.
FIG. 27 is a perspective view of a building with glass windows
according to an exemplary embodiment.
FIG. 28 is a perspective view of a display on a countertop
according to an exemplary embodiment.
FIG. 29 is an exploded perspective view of a consumer electronic
device or product including glass or glass-ceramic articles
according to an exemplary embodiment.
FIG. 30 is a perspective view of a glass or glass-ceramic article
or sheet according to an exemplary embodiment.
DETAILED DESCRIPTION
Applicant has recognized a need for improvements in thermal
processing of cover glass, both in methods and systems for
thermally strengthening cover glass and the resulting thermally
strengthened cover glass sheets themselves. For example, thinner,
but strong optical-quality cover glass sheet materials and products
comprising such cover glass sheets are useful for a number of
applications, including portable electronic devices, consumer
electronic products, cover glass, back glass, etc. Glass is very
strong in compression but relatively weak against tension at the
surface. By providing compression at the surface of a sheet,
balanced by tension at the center where there is no exposed
surface, the useful strength of a cover glass sheet is dramatically
increased. However, while traditional thermal strengthening of
cover glass is generally cheaper and faster relative to alternative
methods of strengthening (e.g., chemical strengthening,
lamination-based strengthening), traditional thermal strengthening
of cover glass is not known to be effective for strengthening thin
cover glass (e.g., cover glass sheets of 2-3 mm or less).
Traditional thermal cover glass strengthening methods are typically
thought to be limited to thicker cover glass sheets because the
level of strengthening depends on the temperature difference
created between the surface and the center of the cover glass sheet
during quenching; and because of thermal conduction rate
limitations of traditional strengthening methods, it is difficult
to achieve significant temperature differences between the surface
and the center of a thin cover glass sheet due to the relatively
even cooling that typically occurs throughout a thin glass
sheet.
On the other hand, strengthening thin cover glass through ion
exchange can be time-consuming and cumbersome, such as requiring
chemical bathing of the cover glass for extended periods of time.
Laminating different types of cover glasses directly to one another
may require complicated manufacturing processes, such as involving
a dual-isopipe fusion draw.
Therefore, a need exists for cover glass or glass-ceramic articles
having stress profiles that result in strengthening of the cover
glass for a variety of uses such as in windows, countertops,
devices, etc. made by processes that are less resource-intensive
and/or cumbersome than conventional processes. Specifically,
processes and systems discussed herein form cover glass articles
having stress profiles that strengthen the exterior portions of the
cover glass, which in turn act to mitigate cracking and damage
while at the same time allowing for a variety of other desirable
cover glass qualities (e.g., geometry, surface quality,
transmittance of visible light, flexibility, etc.) to facilitate
the use in various cover glass or consumer electronic product
applications.
The present description provides improved methods and systems for
utilizing thermal strengthening to produce highly strengthened
cover glass materials, and in particular highly strengthened thin
cover glass sheets. The methods and systems solve a variety of the
limitations of conventional cover glass strengthening processes,
allowing for high levels of strengthening in cover glass sheets
with thicknesses less than about 3 mm, less than 2 mm, less than
1.5 mm, less than 1.0 mm, less than 0.5 mm, less than about 0.25
mm, and less than about 0.1 mm. In particular, Applicant has
developed a system and method that provides a very high rate of
thermal conduction forming a large enough temperature differential
between the surface and center of a cover glass sheet to provide
strengthening or tempering even in very thin cover glass
sheets.
Overview of Conventional Thermal Tempering Technology and
Limitations
Conventional industrial processes for thermally strengthening glass
involve heating glass sheets in a radiant energy furnace or a
convection furnace (or a "combined mode" furnace using both
techniques) to a predetermined temperature, then gas cooling
("quenching"), typically via convection by blowing large amounts of
ambient air against or along the glass surface. This gas cooling
process is predominantly convective, whereby the heat transfer is
by mass motion (collective movement) of the fluid, via diffusion
and advection, as the gas carries heat away from the hot glass
sheet.
In conventional tempering processes, certain factors can restrict
the amount of strengthening typically consider possible in glass
sheets, particularly thin glass sheets. Limitations exist, in part,
because the amount of compressive stress on the finished sheet is
related directly to the size of the temperature differential
between the surface and the center of the sheet, achieved during
quenching. However, the larger the temperature differential during
quenching, the more likely glass is to break during quenching.
Breakage can be reduced, for a given rate of cooling, by starting
the quench from a higher initial glass temperature. Also, higher
starting temperatures typically allow the tempered glass sheet to
achieve the full strengthening potential provided by high cooling
rates. However, increasing the temperature of the sheet at the
start of the quench also has its own potential drawbacks. For
example, high initial glass temperatures can lead to excessive
deformation of the sheet as it becomes softer, again limiting the
practically achievable temperature differential.
In conventional tempering processes, sheet thickness also imposes
significant limits on the achievable temperature differential
during quenching. The thinner the sheet, the lower the temperature
differential between the surface and the center for a given cooling
rate during quenching. This is because there is less glass
thickness to thermally insulate the center from the surface.
Accordingly, thermal strengthening of thin glass typically requires
higher cooling rates (as compared to thermal strengthening of
thicker glass) and, thus, faster removal of heat from the external
surfaces of the glass typically requires significant energy
consumption in order to generate strengthening levels of
differential temperature between the inner and outer portions of
the glass sheet.
By way of example, FIG. 1 shows the power required by air blowers
(in kilowatts per square meter of glass sheet area) employed to
blow sufficient ambient air to "fully temper" soda-lime glass
("SLG"), as a function of glass thickness in millimeters, based on
industry standard thermal strengthening processes developed 35
years ago. The power required increases exponentially as the glass
used gets thinner. Thus, glass sheets of about 3 mm in thickness
were the thinnest fully thermally tempered commercial glass
available for many years.
Further, the thinner the sheet, the greater the likelihood of
deformation at a given softness (that is, at a given viscosity) of
the glass. Therefore, decreasing thickness both reduces the
achievable temperature differential directly and, because of
increased risk of deformation of the sheet, tends to reduce the
opportunity to use higher sheet temperatures to achieve the full
benefits of higher cooling rates and to prevent glass breakage
caused by higher cooling rates. Thus, in conventional convective
gas glass strengthening processes, higher rates of cooling are
achieved by increasing the rate of air flow, decreasing the
distance of air nozzle openings to the glass sheet surface,
increasing the temperature of the glass (at the start of cooling),
and optionally, decreasing the temperature of the cooling air.
As a more recent example, the performance curves of FIG. 2 (Prior
Art) were published using state of the art glass thermal
strengthening equipment. This improved equipment continues to use
traditional air blown convective processes to cool the glass, but
replaces rollers used to support the glass during heating with a
system that utilizes air to support the glass during at least the
last stages of heating. Without roller contact, the glass can be
heated to higher temperatures (and higher softness/lower viscosity)
prior to quenching, reportedly allowing the production of fully
tempered glass at 2 mm thickness. As shown in FIG. 2, the reported
blower power required to strengthen a 2 mm thick sheet is reduced
from 1200 kW/m.sup.2 to 400 kW/m.sup.2 at the higher temperatures
enabled by using air to support the glass (curve N) as compared to
using rollers (curve O).
Although it represents progress to be able to produce fully
tempered 2 mm thick glass, scaling the old and new curves O and N
of FIG. 2 to match the scale of FIG. 1, as shown in FIG. 3 (Prior
Art), shows that the improvement in performance achieved by the
state of the art convective tempering process (shown in FIG. 2) is
relatively small and simply an incremental change in the previous
understanding of the energy needs in convective strengthening of
glass sheets. In FIG. 3 the old and new curves O and N of FIG. 2
are scaled to match the graph of FIG. 1, and overlaid thereon (with
the old curve O truncated at the top at 240 kW/m.sup.2 for easier
viewing of the new curve N). From FIG. 3 it is apparent that the
technology represented by the curve N changes only slightly the
performance curve of convective gas quenching processes as glass
thickness is decreased from 3 mm to 2 mm. The high operating point
(400 kW/m.sup.2 of blower power for 2 mm glass) shows the extreme
increase in power still required to process thinner glass by this
method. The sharp increase in airflow and, thus, power needed
suggests the difficulty, as a matter of both engineering practice
and economics, in going below 2 mm thickness while producing fully
tempered glass using conventional convective gas strengthening
methods. Additionally, the very high airflows needed also could
deform the shape of thinner sheets. Accordingly, to reach full
temper of glass having a thickness of less than 2 mm or to reach
full temper at 2 mm in glasses having coefficients of thermal
expansion ("CTE") lower than that of soda-lime glasses using
thermal tempering, Applicant has identified that another tempering
method/system is needed.
Alternative thermal strengthening methods to current commercial
convective gas strengthening have been tried as well, but each has
certain drawbacks relative to convective gas strengthening. In
particular, typical alternative thermal strengthening methods that
achieve higher cooling rates generally require at least some liquid
or solid contact with the glass surfaces, rather than gas contact
only. Such contact with the glass sheet can adversely affect glass
surface quality, glass flatness, and/or evenness of the
strengthening process. These defects sometimes can be perceived by
the human eye, particularly when viewed in reflected light. As
described in more detail below, at least in some embodiments, the
conductive thermal tempering system of the present disclosure
reduces or eliminates such contact-related defects.
Liquid contact strengthening, in the form of immersion in liquid
baths or flowing liquids, as well as in the form of spraying, has
been used to achieve higher cooling rates than convective gas
strengthening, but has the drawback of causing excessive thermal
variations across a sheet during the cooling process. In immersion
or immersion-like spraying or flowing of liquids, large thermal
variations over small areas can occur due to convection currents
that arise spontaneously within the liquid bath or liquid flow. In
finer spraying, the discrete spray droplets and the effects of
nozzle spray patterns also produce significant thermal variations.
Excessive thermal variations tend to cause glass breakage during
thermal strengthening by liquid contact, which can be mitigated by
limiting the cooling rates, but limiting cooling rates also lowers
the resulting strengths that can be achieved. Further, the
necessary handling of the sheet (to position or hold it within the
liquid bath or liquid flow or liquid spray) also causes physical
stress and excessive thermal variations from physical contact with
the sheet, tending also to cause breakage during strengthening and
limiting the cooling rates and resulting strengths. Finally, some
liquid cooling methods, such as high cooling rate quenching by oil
immersion and various spraying techniques, can alter the glass
surface during such cooling, requiring later removal of glass
material from the sheet surface to produce a satisfactory
finish.
Solid contact thermal strengthening involves contacting the surface
of the hot glass with a cooler solid surface. As with liquid
contact strengthening, excessive thermal variations, like those
seen in liquid contact strengthening, can easily arise during the
quenching process. Any imperfection in the surface finish of the
glass sheet, in the quenching surfaces, or in the consistency of
the thickness of the sheet, results in imperfect contact over some
area of the sheet, and this imperfect contact may cause large
thermal variations that tend to break the glass during processing
and may also cause unwanted birefringence if the sheet survives.
Additionally, contacting the hot glass sheet with a solid object
can lead to the formation of surface defects, such as chips,
checks, cracks, scratches, and the like. Achieving good physical
contact over the entirety of the surfaces of a glass sheet also can
become increasing difficult as the dimensions of the sheet
increase. Physical contact with a solid surface also can
mechanically stress the sheet during quenching, adding to the
likelihood of breaking the sheet during the process. Further, the
extreme high rate temperature changes at the initiation of contact
can cause breakage during sheet processing and, as such, contact
cooling of thin glass substrates has not been commercially
viable.
Overview of Applicant's Thermally Strengthened Cover Glass and
Related Conductive Cooling Process and Method
The present disclosure surpasses the traditional processes
described above to effectively, efficiently, and evenly thermally
strengthen thin cover glass sheets at commercial scales without
generating various flaws common in conventional processes, e.g.,
without damaging the surface of the cover glass, without inducing
birefringence, without uneven strengthening, and/or without causing
unacceptable breakage, etc. Previously unobtainable, thin,
thermally tempered/strengthened cover glass sheets can be produced
by one or more of the embodiments disclosed herein. The systems and
processes discussed herein accomplish this by providing very high
heat transfer rates in a precise manner, with good physical control
and gentle handling of the cover glass. In particular embodiments,
the processes and systems discussed herein utilize a small-gap, gas
bearing in the cooling/quenching section that Applicant has
identified as allowing for processing thin cover glass sheets at
higher relative temperatures at the start of cooling, resulting in
higher thermal strengthening levels. As described below, this
small-gap, gas bearing cooling/quenching section achieves very high
heat transfer rates via conductive heat transfer to heat sink(s)
across the gap, rather than using high air flow based convective
cooling. This high rate conductive heat transfer is achieved while
not contacting the cover glass with liquid or solid material, by
supporting the cover glass on gas bearings within the gap. As
described below, Applicant has also identified that, in at least
some embodiments, the processes and systems discussed herein form
thermally strengthened cover glass, specifically thermally
strengthened thin cover glass (e.g, for consumer electronic
products), having one or more unique properties.
Some embodiments of cover glass sheets treated by methods and/or
systems according to the present disclosure have higher levels of
permanent thermally induced stresses than previously known. Without
wishing to be bound by theory, it is believed that the achieved
levels of thermally induced stress are obtainable for a combination
of reasons. The high uniformity of the heat transfer in the
processes detailed herein reduces or removes physical and unwanted
thermal stresses in the cover glass, allowing consumer electronic
glass sheets to be tempered at higher heat transfer rates without
breaking. Further, the present methods can be performed at lower
glass sheet viscosities (higher initial temperatures at the start
of quench), while still preserving the desired cover glass flatness
and form, which provides a much greater change in temperature in
the cooling process, thus increasing the heat strengthening levels
achieved.
Thermally Tempered Cover Glass Sheet
As noted above, Applicant has developed a system and process for
forming thermally strengthened cover glass sheets, particularly
thin cover glass sheets, and as discussed in this section, the
thermally strengthened, thin cover glass sheets formed as discussed
herein have one or more unique properties and/or combinations of
properties, previously unachievable through conventional thermal or
other tempering methods. The thermally tempered cover glass or
consumer electronic glass of the present disclosure may be used in
a variety of consumer electronic products (e.g., computers,
tablets, personal handheld devices, touch sensitive displays,
household appliances, mobile phones, portable media players,
televisions, notebook computers, watches, tablet computers,
etc.).
Thermally Tempered Cover Glass Sheet Structure and Dimensions
Referring to FIG. 4 and FIG. 5, a thermally strengthened cover
glass sheet having a high surface compressive stress and/or a high
central tension is shown according to an exemplary embodiment. FIG.
4 shows a perspective view of a thermally strengthened cover glass
or glass-ceramic article or sheet 500, and FIG. 5 is a diagrammatic
partial cross-section of thermally strengthened cover glass sheet
500 according to one or more embodiments.
As shown in FIG. 4, a strengthened cover glass or glass-ceramic
article 500 (e.g., sheet, beam, plate), includes a first major
surface 510, a second major surface 520 (dotted line to back side
of the sheet 500, which may be translucent as disclosed herein),
and a body 522 extending therebetween. The second major surface 520
is on an opposite side of the body 522 from the first major surface
510 such that a thickness t of the strengthened cover glass or
glass-ceramic sheet 500 is defined as a distance between the first
and second major surfaces 510, 520, where the thickness t is also a
dimension of depth. A width, w, of the strengthened cover glass or
glass-ceramic sheet 500 is defined as a first dimension of one of
the first or second major surfaces 510, 520 orthogonal to the
thickness t. A length, l, of the strengthened cover glass or
glass-ceramic sheet 500 is defined as a second dimension of one of
the first or second major surfaces 510, 520 orthogonal to both the
thickness t and the width w.
In exemplary embodiments, thickness t of cover glass sheet 500 is
less than length l of cover glass sheet 500. In other exemplary
embodiments, thickness t of cover glass sheet 500 is less than
width w of cover glass sheet 500. In yet other exemplary
embodiments, thickness t of cover glass sheet 500 is less than both
length l and width w of cover glass sheet 500. As shown in FIG. 5,
cover glass sheet 500 further has regions of permanent thermally
induced compressive stress 530 and 540 at and/or near the first and
second major surfaces 510, 520, balanced by a region of permanent
thermally induced central tensile stress 550 (i.e., tension) in the
central portion of the sheet.
The methods and systems may be used to form strengthened cover
glass sheets having a wide variety of thickness ranges. In various
embodiments, thickness t of cover glass sheet 500 ranges from 0.1
mm to 5.7 or 6.0 mm, including, in addition to the end point
values, 0.2 mm, 0.28 mm, 0.4 mm, 0.5 mm, 0.55 mm, 0.7 mm, 1 mm, 1.1
mm, 1.5 mm, 1.8 mm, 2 mm, and 3.2 mm. Contemplated embodiments
include thermally strengthened cover glass sheets 500 having
thicknesses t in ranges from 0.1 to 20 mm, from 0.1 to 16 mm, from
0.1 to 12 mm, from 0.1 to 8 mm, from 0.1 to 6 mm, from 0.1 to 4 mm,
from 0.1 to 3 mm, from 0.1 to 2 mm, from 0.1 to less than 2 mm,
from 0.1 to 1.5 mm, from 0.1 to 1 mm, from 0.1 to 0.7 mm, from 0.1
to 0.5 mm and from 0.1 to 0.3 mm.
In some embodiments, cover glass sheets of 3 mm or less in
thickness are used. In some embodiments, the cover glass thickness
is about (e.g., plus or minus 1%) 8 mm or less, about 6 mm or less,
about 3 mm or less, about 2.5 mm or less, about 2 mm or less, about
1.8 mm or less, about 1.6 mm or less, about 1.4 mm or less, about
1.2 mm or less, about 1 mm or less, about 0.8 mm or less, about 0.7
mm or less, about 0.6 mm or less, about 0.5 mm or less, about 0.4
mm or less, about 0.3 mm or less, or about 0.28 mm or less.
In some embodiments, thermally strengthened cover glass sheets have
high aspect ratios--i.e., the length and width to thickness ratios
are large. Because the thermal tempering processes discussed herein
do not rely on high pressures or large volumes of air, various
cover glass sheet properties, such as surface roughness and
flatness, can be maintained after tempering by the use of gas
bearings and high thermal transfer rate systems discussed herein.
Similarly, the thermal tempering processes discussed herein allow
high aspect ratio cover glass sheets (i.e., cover glass sheets with
high ratio of length to thickness, or of width to thickness, or
both) to be thermally strengthened while retaining the desired or
necessary shape. Specifically, sheets with length to thickness
and/or width to thickness ratios ("aspect ratios") of approximately
at least 10:1, at least 20:1, and up to and over 1000:1 can be
strengthened. In contemplated embodiments, sheets with aspect
ratios of at least 200:1, at least 500:1, at least 1000:1, at least
2000:1, at least 4000:1 can be strengthened.
According to an exemplary embodiment, the length l of the
strengthened cover glass or glass-ceramic sheet 500 is greater than
or equal to the width w, such as greater than twice the width w,
greater than five times the width w, and/or no more than fifty
times the width w. In some such embodiments, the width w of the
strengthened cover glass or glass-ceramic sheet 500 is greater than
or equal to the thickness t, such as greater than twice the
thickness t, greater than five times the thickness t, and/or no
more than fifty times the thickness t.
In some embodiments, such as for applications disclosed with regard
to FIGS. 27-30 discussed below, for example, the length l of the
cover glass or glass-ceramic sheet 500 is at least 1 cm, such as at
least 3 cm, at least 5 cm, at least 7.5 cm, at least 20 cm, at
least 50 cm, and/or no more than 50 m, such as no more than 10 m,
no more than 7.5 m, no more than 5 m. In some such embodiments, the
width w of the cover glass or glass-ceramic sheet 500 is at least 1
cm, such as at least 3 cm, at least 5 cm, at least 7.5 cm, at least
20 cm, at least 50 cm, and/or no more than 50 m, such as no more
than 10 m, no more than 7.5 m, no more than 5 m. Referring to FIG.
4, cover glass or glass-ceramic is in the form a sheet 500 has a
thickness t that is thinner than 5 cm, such as 2.5 cm or less, 1 cm
or less, 5 mm or less, 2.5 mm or less, 2 mm or less, 1.7 mm or
less, 1.5 mm or less, 1.2 mm or less, or even 1 mm or less in
contemplated embodiments, such as 0.8 mm or less; and/or the
thickness t is at least 10 .mu.m, such as at least 50 m, at least
100 m, at least 300 m.
In other contemplated embodiments, the cover glass or glass-ceramic
article may be sized other than as disclosed herein. In
contemplated embodiments, the length l, width w, and/or thickness t
of the cover glass or glass-ceramic articles may vary, such as for
more complex geometries (see generally FIG. 30), where dimensions
disclosed herein at least apply to aspects of the corresponding
cover glass or glass-ceramic articles having the above-described
definitions of length l, width w, and thickness t with respect to
one another.
In some embodiments, at least one of the first or second surfaces
510, 520 of cover glass sheet 500 has a relatively large surface
area. In various embodiments, first and/or second surfaces 510, 520
having areas of at least 100 mm.sup.2, such as at least 900
mm.sup.2, at least 2500 mm.sup.2 at least 5000 mm.sup.2, at least
100 cm.sup.2, at least 900 cm.sup.2, at least 2500 cm.sup.2, at
least 5000 cm.sup.2, and/or no more than 2500 m.sup.2, such as no
more than 100 m.sup.2, no more than 5000 cm.sup.2, no more than
2500 cm.sup.2, no more than 1000 cm.sup.2, no more than 500
cm.sup.2, no more than 100 cm.sup.2. As such, the cover glass or
glass-ceramic sheet 500 may have a relatively large surface area;
which, except by methods and systems disclosed herein, may be
difficult or impossible to thermally strengthen particularly while
having the thicknesses, surface qualities, and/or strain
homogeneities of the cover glass sheets discussed herein. Further,
except by methods and systems disclosed herein, it may be difficult
or impossible to achieve the stress profile, particularly the
negative tensile stress portion of the stress profile (see
generally FIG. 6), without relying upon ion-exchange or a change in
the type of cover glass.
Thermally Strengthened Cover Glass Sheet Compressive and Tensile
Stresses
As noted above, the thermally strengthened cover glass sheets
discussed herein may have surprisingly high surface compressive
stresses, e.g., in regions 530, 540 shown in FIG. 5, surprisingly
high central tensile stresses, e.g., in region 550 shown in FIG. 5,
and/or unique stress profiles (see FIG. 6). This is particularly
true considering the low thickness and/or other unique physical
properties (e.g., very low roughness, high degree of flatness,
various optical properties, fictive temperature properties, etc.)
of cover glass sheet 500 as discussed herein.
Compressive stresses of cover glasses (e.g., in regions 530, 540
shown in FIG. 5) formed by the processes and systems disclosed
herein can vary as a function of thickness t of the cover glasses.
In various embodiments, cover glasses, e.g., cover glass sheet 500,
having a thickness of 3 mm or less have a compressive stress (e.g.,
surface compressive stress) of at least 80 MPa, at least 100 MPa,
at least 150 MPa, at least 200 MPa, at least 250 MPa, at least 300
MPa, at least 350 MPa, at least 400 MPa, and/or no more than 1 GPa.
In contemplated embodiments, cover glasses having a thickness of 2
mm or less have a compressive stress of at least 80 MPa, at least
100 MPa, at least 150 MPa, at least 175 MPa, at least 200 MPa, at
least 250 MPa, at least 300 MPa, at least 350 MPa, at least 400
MPa, and/or no more than 1 GPa. In contemplated embodiments, cover
glasses having a thickness of 1.5 mm or less have a compressive
stress of at least 80 MPa, at least 100-MPa, at least 150 MPa, at
least 175 MPa, at least 200 MPa, at least 250 MPa, at least
300-MPa, at least 350 MPa, and/or no more than 1 GPa. In
contemplated embodiments, cover glasses having a thickness of 1 mm
or less have a compressive stress of at least 80 MPa, at least 100
MPa, at least 150 MPa, at least 175 MPa, at least 200 MPa, at least
250 MPa, at least 300 MPa, and/or no more than 1 GPa. In
contemplated embodiments, cover glasses having a thickness of 0.5
mm or less have a compressive stress of at least 50 MPa, at least
80 MPa, at least 100 MPa, at least 150 MPa, at least 175 MPa, at
least 200 MPa, at least 250 MPa, and/or no more than 1 GPa.
In some embodiments, the thermally induced central tension in cover
glasses formed by the processes and systems disclosed herein (e.g.,
in the region 550 shown in FIG. 5) may be greater than 40 MPa,
greater than 50 MPa, greater than 75 MPa, greater than 100 MPa. In
other embodiments, the thermally induced central tension may be
less than 300 MPa, or less than 400 MPa. In some embodiments, the
thermally induced central tension may be from about 50 MPa to about
300 MPa, about 60 MPa to about 200 MPa, about 70 MPa to about 150
MPa, or about 80 MPa to about 140 MPa. In some embodiments, the
thermally strengthened cover glass sheets have high thinness i.e.,
are particularly thin. Because very high-heat transfer rates can be
applied via the systems and methods discussed herein, significant
thermal effects, for example central tensions of at least 10 or
even at least 20 MPa, can be produced in sheets of SLG of less than
0.3 mm thickness. In fact, very thin sheets, sheets at least as
thin as 0.1 mm, can be thermal strengthened. Specific levels of
thermal stresses achieved and achievable, considered as a function
of thickness and other variables, are described in further detail
herein.
Referring to FIG. 6, a conceptual stress profile 560, at room
temperature of 25.degree. C. and standard atmospheric pressure, of
the strengthened cover glass or glass-ceramic sheet 500 of FIG. 4,
shows an interior portion 550 of the strengthened cover glass or
glass-ceramic sheet 500 under positive tensile stress and portions
530, 540 of the strengthened cover glass or glass-ceramic sheet 500
exterior to and adjoining the interior portion 550 under negative
tensile stress (e.g., positive compressive stress). Applicant
believes that the negative tensile stress at least in part
fortifies the strengthened cover glass or glass-ceramic sheet 500
by limiting initiation and/or propagation of cracks
therethrough.
Believed unique to the present inventive technology, given
relatively large surface areas and/or thin thicknesses of the
strengthened cover glass or glass-ceramic sheet 500 as disclosed
herein, tensile stress in the stress profile 560 sharply
transitions between the positive tensile stress of the interior
portion 550 and the negative tensile stress of the portions 530,
540 exterior to and adjoining the interior portion 550. This sharp
transition may be understood as a rate of change (i.e., slope) of
the tensile stress which may be expressed as a magnitude of stress
(e.g., 100 MPa, 200 MPa, 250 MPa, 300 MPa, 400 MPa, a difference in
peak values of the positive and negative tensile stresses +.sigma.,
-.sigma.) divided by a distance of thickness over which the change
occurs, such as a distance of 1 mm, such as a distance of 500
.mu.m, 250 .mu.m, 100 .mu.m (which is the distance used to quantify
a rate of change, which may be a portion of article thickness, and
not necessarily a dimension of the article geometry). In some such
embodiments, the rate of change of the tensile stress does not
exceed 7000 MPa divided by 1 mm, such as no more than 5000 MPa
divided by 1 mm. In contemplated embodiments, the difference in
peak values of the positive and negative tensile stresses is at
least 50 MPa, such as at least 100 MPa, at least 150 MPa, at least
200 MPa, at least 250 MPa, at least 300 MPa, at least 400 MPa, at
least 500 MPa, and/or no more than 50 GPa. In contemplated
embodiments, the cover glass or glass-ceramic sheet 500 has a peak
negative tensile stress of at least 50 MPa in magnitude, such as at
least 100 MPa, at least 150 MPa, at least 200 MPa, at least 250
MPa, at least 300 MPa, at least 400 MPa, at least 500 MPa. The
steep tensile curve transitions generated by the system and method
discussed herein are believed to be indicative of the ability to
achieve higher magnitudes of negative tensile stress at a surface
of a cover glass sheet for a given thickness and/or to manufacture
thinner cover glass articles to a higher degree of negative tensile
stress, such as to achieve a fragmentation potential for dicing as
disclosed herein. Conventional thermal tempering approaches may be
unable to achieve such steep tensile stress curves.
According to an exemplary embodiment, the high rate of change of
tensile stress is at least one of the above-described magnitudes or
greater sustained over a thickness-wise stretch of the stress
profile 560 that is at least 2% of the thickness, such as at least
5% of the thickness, at least 10% of the thickness, at least 15% of
the thickness, or at least 25% of the thickness of cover glass
sheet 500. In contemplated embodiments, the strengthening extends
deep into the strengthened cover glass or glass-ceramic sheet 500
such that the thickness-wise stretch with the high rate of change
of tensile stress is centered at a depth of between 20% and 80%
into the thickness from the first surface, which may further
distinguish chemical tempering for example.
In at least some contemplated embodiments, the strengthened cover
glass or glass-ceramic article includes a change in the composition
thereof in terms of ion content, conceptually shown as dotted line
562 in FIG. 6. More specifically, the composition of the
strengthened cover glass or glass-ceramic article 500 in such
embodiments includes exchanged or implanted ions that influence the
stress profile 560. In some such embodiments, the exchanged or
implanted ions do not extend fully through the portions 530, 540 of
the strengthened cover glass or glass-ceramic article 500 under the
negative tensile stress because the negative tensile stress is also
a result of the thermal tempering as disclosed herein.
Accordingly, the curve of the tensile stress profile 560 with ion
exchange strength augmentation includes a discontinuity or sudden
change 564 in direction where tangents of the curve differ from one
another on either side of the discontinuity or sudden change 564.
The sudden change 564 is located within the portions 530, 540 under
negative tensile stress such that the tensile stress is negative on
either side immediately adjacent to the discontinuity or sudden
change 564. The discontinuity or sudden change 564 may correspond
to the depth of the different ion content, however in some such
embodiments other parts of the portions 530, 540 under negative
tensile stress still have the same composition in terms of ion
content as the portion 550 under positive tensile stress.
Put another way, for at least some strengthened cover glass or
glass ceramic articles 500, with or without ion-exchange or
implantation, the composition of at least a part of the portions
530, 540 of the strengthened cover glass or glass-ceramic sheet
500, which is under the negative tensile stress and is exterior to
and adjoining the interior portion 550, is the same as the
composition of at least a part of the interior portion 550, which
is under the positive tensile stress. In such embodiments, at least
some of the negative tensile stress of the stress profile is
independent of a change in the composition (e.g., ion composition)
of the strengthened cover glass or glass-ceramic sheet 500. Such
structure may simplify the composition of the strengthened cover
glass or glass-ceramic sheet 500 at least to a degree by providing
sufficient strength without and/or with less chemical tempering.
Further, such structure may reduce stress concentrations within the
strengthened cover glass or glass-ceramic sheet 500 due to
discontinuity/changes in composition, possibly reducing chances of
delamination and/or cracking at the composition discontinuity.
Thermally Tempered Cover Glass Sheet Break Performance
If sufficient energy is stored in the region of tensile stress 550,
the cover glass will break like safety glass or "dice" when
sufficiently damaged. As used herein, a cover glass sheet is
considered to dice when an area of the cover glass sheet 25
cm.sup.2 breaks into 40 or more pieces. In some embodiments, dicing
is used as a qualitative measure of showing that the cover glass
sheet is "fully tempered" (i.e., for 2 mm or thicker cover glass,
where the cover glass sheet has a compressive stress of at least 65
MPa or an edge compression of at least 67 MPa). In various
embodiments, cover glass sheet 500 has sufficient tensile stress in
region of tensile stress 550 such that a 25 cm.sup.2 piece of cover
glass sheet 500 breaks into 40 or more pieces.
Referring to FIG. 7, a cover glass or glass-ceramic article 610,
having properties as disclosed herein with respect to the cover
glass or glass-ceramic sheets, such as sheet 500, has been
fractured, such as using a prick punch or other instrument and/or
generally in accordance with American National Standards Institute
(ANSI) Z97.1 (impact test) and the ASTM 1048 standard. According to
an exemplary embodiment, the cover glass or glass ceramic article
610 has been strengthened to a degree that dicing has occurred upon
the fracture, forming a plurality of small granular chunks 616
(e.g., fragments, pieces). In some embodiments, the cover glass or
glass-ceramic article 610 has a thermally-induced stress sufficient
to produce a number of granular chunks 616 that is not less than 40
within an area of 50-by-50 mm of the cover glass or glass-ceramic
article 610 in a fragmentation test in which an impact is applied
with a hammer or a punch to initiate cracking of the cover glass
into granular pieces. A standard office thumb tack 612, with a
metal pin length 614 of about 1 cm is shown for reference.
According to various contemplated embodiments, despite the thin
thickness of the strengthened cover glass or glass-ceramic article
610, the stress profile (see generally FIG. 6) imparts a high
fragmentation potential of the strengthened cover glass or
glass-ceramic article 610 such that when fractured the strengthened
cover glass or glass-ceramic article 610 shatters into particularly
small granular chunks 616, those having an area on either the first
or second surface of less than 90 mm.sup.2, such as less than 50
mm.sup.2, such as less than 20 mm.sup.2, such as less than 10
mm.sup.2, such as less than 5 mm.sup.2, and/or at least 10
.mu.m.sup.2. In some such embodiments, the fragmentation potential
of the strengthened cover glass or glass-ceramic article 610 is
such that at least 20% (e.g., at least 50%, at least 70%, at least
95%) of the granular chunks 616 have an area of at least one of the
first or second surfaces of one of the above-described amounts when
the strengthened cover glass or glass-ceramic article is
fractured.
Due at least in part to the particularly thin geometry of the cover
glass or glass-ceramic article 610 that may be manufactured with
the tensile stresses as disclosed herein using the inventive
technology in some embodiments, the fragmentation potential of the
strengthened cover glass or glass-ceramic article 610 is such that,
when fractured, the strengthened cover glass or glass-ceramic
article 610 shatters into particularly low-volume granular chunks,
those having a volume of less than 50 mm.sup.3, such as less than
40 mm.sup.3, such as less than 30 mm.sup.3, such as less than 25
mm.sup.3, and/or at least a volume of 50 .mu.m.sup.3.
Due at least in part to the particularly large area of the cover
glass or glass-ceramic article 610 that may be manufactured with
the tensile stresses as disclosed herein using the inventive
technology in some embodiments, the fragmentation potential of the
strengthened cover glass or glass-ceramic article 610 is such that,
when fractured, the strengthened cover glass or glass-ceramic
article 610 shatters into at least 100 granular chunks 616 of at
least of 50 .mu.m.sup.3 in volume, such as at least 200, at least
400, at least 1000, at least 4000 granular chunks 616 of at least
of 50 .mu.m.sup.3 in volume.
Referring now to FIG. 8 and FIG. 9, experiments were performed on
1.1 mm thick glass sheets of glass comprising at least 70% silicon
dioxide by weight, and/or at least 10% sodium oxide by weight,
and/or at least 7% calcium oxide by weight, and strengthened using
the equipment and processes disclosed herein. As shown in FIG. 8,
the number of granular chunks 616 per square centimeter of the
glass has been found to be generally related to the magnitude of
positive tensile stress at the center of the respective cover glass
or glass-ceramic article 610. Similarly, as shown in FIG. 9, the
fragmentation potential of the respective cover glass or
glass-ceramic article 610 has also been found to be related to
temperature of the glass in the hot zone (see e.g., FIG. 21, FIG.
22 and FIG. 23) and the calculated expected heat transfer
coefficient (h) in units of cal/cm.sup.2s.degree. C. (SI units
watt/m.sup.2.degree. K) effectively applied to the cover glass
surfaces during quenching, based on size of the gap between the
glass sheet surfaces and the heat sink/gas bearing during quenching
and on the thermal conductivity of the gas used in the gap.
Thermally Tempered Cover Glass Sheet Fictive Temperature
In various embodiments, the thermally strengthened cover glass
sheets formed by the systems and methods discussed herein (e.g.,
cover glass sheet 500) have high fictive temperatures. It will be
understood that in various embodiments, high fictive temperatures
of the cover glass materials discussed herein relate to the high
level of tempering, high central tensile stresses and/or high
compressive surface stress of cover glass sheet 500. Surface
fictive temperatures may be determined by any suitable method,
including differential scanning calorimetry, Brillouin
spectroscopy, or Raman spectroscopy.
According to an exemplary embodiment, the cover glass or
glass-ceramic sheet 500 has a portion thereof, such as at or near
the first and/or second surfaces 510, 520, that has a particularly
high fictive temperature, such as at least 500.degree. C., such as
at least 600.degree. C., or even at least 700.degree. C. in some
embodiments, such as for soda-lime glass. According to an exemplary
embodiment, the cover glass or glass-ceramic sheet 500 has a
portion thereof, such as at or near the first and/or second
surfaces 510, 520, that has a particularly high fictive temperature
relative to annealed glass of the same chemical composition, such
as at least 10.degree. C. greater, at least 30.degree. C. greater,
at least 50.degree. C. greater, at least 70.degree. C. greater, or
even at least 100.degree. C. greater. High fictive temperature may
be achieved by the presently disclosed inventive technology at
least in part due to the rapid transition from the hot to the
cooling zones in the strengthening system (see e.g., FIG. 21, FIG.
22 and FIG. 23). Applicant believes that high fictive temperature
may correspond or relate to increased damage resistance of
glass.
In some methods of determining surface fictive temperatures, it may
be necessary to break the glass to relieve the "temper stresses"
induced by the heat strengthening process in order to measure
fictive temperature with reasonably accuracy. It is well known that
characteristic structure bands measured by Raman spectroscopy shift
in a controlled manner both with respect to the fictive temperature
and with respect to applied stress in silicate glasses. This shift
can be used to non-destructively measure the fictive temperature of
a thermally strengthened cover glass sheet if the temper stress is
known.
Referring generally to FIG. 10, determination of fictive
temperature for several exemplary cover glass articles is shown.
Stress effects on the Raman spectrum of silica glass are reported
in D. R. Tallant, T. A. Michalske, and W. L. Smith, "The effects of
tensile stress on the Raman spectrum of silica glass," J.
Non-Cryst. Solids, 106 380-383 (1988). Commercial glasses of 65 wt.
% silica or more have substantially the same response. Although the
reported stress response is for uniaxial stress, in the case of a
unibiaxial stress state such as that which is observed in tempered
glass, .sigma..sub.xx=.sigma..sub.yy, the peak can be expected to
shift by twice that expected by a uniaxial stress. The peak near
1090 cm.sup.-1 in soda-lime glass and in glass 2 corresponds to the
1050 cm.sup.-1 peak observed in silica glass. The effects of stress
on the 1050 cm.sup.-1 peak in silica, and on the corresponding peak
in SLG and other silicate glasses can be expressed, as a function
of stress .sigma. in MPa, by equation a)
.omega.(cm.sup.-1)=1054.93-0.00232.sigma..
A calibration curve was produced of Raman band positions as a
function of the fictive temperature for SLG and another glass,
glass 2. Glass samples were heat-treated for various times, 2-3
times longer than the structural relaxation times calculated by
.tau.=10*.eta./G, where r) is the viscosity, and G the shear
modulus. After heat-treatment, the glasses were quenched in water
to freeze the fictive temperature at the heat-treatment
temperature. The glass surfaces were then measured by micro Raman
at 50.times. magnification and a 1-2 .mu.m spot size using a 442 nm
laser, 10-30 s exposure time, and 100% power, over the range of
200-1800 cm.sup.-1. The position of the peak at 1000-1200 cm.sup.-1
was fit using computer software, Renishaw WiRE version 4.1, in this
case. A good fit of the 1090 cm.sup.-1 Raman peak measured in SLG
on the air side as a function of fictive temperature Tf(in .degree.
C.) is given by equation b) .omega.(cm.sup.-1)=1110.66-0.0282Tf.
For glass 2, a good fit is given by equation c)
.omega.(cm.sup.-1)=1102.00-0.0231Tf.
Using the relationships established in equations a), b), and c), it
is possible to express the fictive temperature of the cover glass
as a function of a measured Raman peak position with a correction
factor due to surface compressive stress. A compressive stress of
100 MPa, .sigma..sub.c, shifts the Raman band position equivalent
to approximately a 15 to 20 degree Celsius reduction in the fictive
temperature. The following equation is applicable to SLG:
.function..degree..times..times..omega..function..times..times..degree..t-
imes..times..function..sigma..function. ##EQU00004##
The equation applicable to glass 2 is:
.function..degree..times..times..omega..function..times..times..degree..t-
imes..times..sigma..function. ##EQU00005##
In these equations, co is the measured peak wavenumber for the peak
near 1090 cm.sup.-1, .sigma..sub.c is the surface compressive
stress measured by any suitable technique, yielding
stress-corrected measurement of fictive temperature in .degree. C.
As a demonstration of increased damage resistance related to the
determined fictive temperature, four glass sheet samples were
prepared, two 6 mm soda-lime glass (SLG) sheets by conventional
tempering methods to approximately 70 and 110 MPa surface
compressive stress (CS), and two 1.1 mm SLG sheets by the methods
and systems disclosed herein to about the same levels of CS. Two
additional sheets, one of each thickness were used as controls. The
surfaces of each test sheet were subjected to standard Vickers
indentation. Various levels of force were applied, for 15 seconds
each, and after a 24 hour wait, indentations were each examined. As
shown in Table I, the 50% cracking threshold (defined as the load
at which the average number of cracks appearing is two out of the
four points of the indenter at which cracks tend to initiate) was
determined for each sample.
Table I shows that the Vickers crack initiation threshold for SLG
processed by conventional convective gas tempering (as reflected in
the 6 mm sheet) is essentially the same as that for annealed or
as-delivered SLG sheets, rising from between zero and one newton
(N) to about one to less than two newtons. This correlates with the
relatively modest rise in surface fictive temperature (T.sub.fs or
Tf.sub.surface) of .about.25 to 35.degree. C. relative to glass
transition temperature (T.sub.g=550.degree. C. for SLG, defined as
.eta.=10.sup.12-13.3 Poise) that was provided by conventional
tempering. In contrast, by tempering using the present methods and
systems, the Vickers crack initiation threshold improved to greater
than 10 N, a 10-fold increase over the Vickers damage resistance
imparted by conventional tempering. In the embodied glasses, the
T.sub.fs minus T.sub.g was at least 50.degree. C., or at least
75.degree. C., or at least 90.degree. C., or in the range of from
approximately 75.degree. C. to 100.degree. C. Even in embodiments
comprising lower levels of heat strengthening, the embodied glasses
can still provide increased resistance, at levels such as 5 N, for
instance. In certain contemplated embodiments, the 50% cracking
threshold after a 15 second Vickers crack initiation test may be
equal to or greater than 5 N, 10 N, 20 N, or 30 N
TABLE-US-00001 TABLE I Cracking Thickness CS Surface T.sub.f
Threshold Sample (mm) (MPa) (.degree. C.) (N) Control 1.1 Annealed
~T.sub.g (550) 0-1 Control 6 Annealed ~T.sub.g (550) 0-1 Thin low
strength 1.1 -72 626 10-20 Thick low strength 6 -66 575 1-2 Thin
medium strength 1.1 -106 642 10-20 Thick medium strength 6 -114 586
1-2
The following non-dimensional fictive temperature parameter .theta.
can be used to compare the relative performance of a thermal
strengthening process in terms of the fictive temperature produced.
Given in terms of surface fictive temperature .theta.s in this
case: .theta.s=(T.sub.fs-T.sub.anneal)/(T.sub.soft-T.sub.anneal)
(3) where T.sub.fs is the surface fictive temperature, T.sub.anneal
(the temperature of the glass at a viscosity of .eta.=10.sup.13.2
Poise) is the annealing point and T.sub.soft (the temperature of
the glass at a viscosity of .eta.=10.sup.7.6 Poise) is the
softening point of the glass of the sheet. FIG. 10 is a plot of
.theta.s for measured surface fictive temperatures as a function of
heat transfer rate, h, applied during thermal strengthening for two
different glasses. As shown in FIG. 10, the results for the two
different glasses overlie each other fairly closely. This means
that parameter .theta. provides a means to compare the fictive
temperatures of different glasses compared directly, in relation to
the heat transfer rate h required to produce them. The vertical
range of results at each h corresponds to variation in the value of
T.sub.0, the initial temperature at the start of quenching. In
embodiments, parameter .theta.s comprises from about (e.g., plus or
minus 10%) 0.2 to about 0.9, or 0.21 to 0.09, or 0.22 to 0.09, or
0.23 to 0.09, or 0.24 to 0.09, or 0.25 to 0.09, or 0.30 to 0.09, or
0.40 to 0.09, or 0.5 to 0.9, or 0.51 to 0.9, or 0.52 to 0.9, or
0.53 to 0.9, or 0.54 to 0.9, or 0.54 to 0.9, or 0.55 to 0.9, or 0.6
to 0.9, or even 0.65 to 0.9.
Thermally Tempered Cover Glass Sheet Temperability Parameter
In various embodiments, the thermally strengthened cover glass
sheets formed by the systems and methods discussed herein (e.g.,
cover glass sheet 500) have a high temperability and/or heat
transfer value. The "specific thermal stress" of a glass is given
by:
.alpha..mu. ##EQU00006## where .alpha. is the (low temperature
linear) CTE of the glass, E is the modulus of elasticity of the
glass material and .mu. is Poisson's ratio of the glass material.
This value is used to indicate the level of stress produced within
a given glass composition when subjected to a temperature gradient.
It may also be used as an estimator of thermal "temperability." At
higher thermal transfer rates (such as at about 800 W/m.sup.2K and
above, for example), however, the high temperature or "liquidus"
CTE of the glass begins to affect tempering performance. Therefore,
under such conditions, the temperability parameter .PSI., based on
an approximation of integration over the changing CTE values across
the viscosity curve, is found to be useful:
.PSI.=E[T.sub.strain.alpha..sub.CTE.sup.s+.alpha..sub.CTE.sup.L(T-
.sub.soft-T.sub.strain)] (5) where .alpha..sup.S.sub.CTE is the low
temperature linear CTE (equivalent to the average linear expansion
coefficient from 0-300.degree. C. for the glass), expressed in
1/.degree. C. (.degree. C..sup.-1), .alpha..sup.L.sub.CTE is the
high temperature linear CTE (equivalent to the high-temperature
plateau value which is observed to occur somewhere between the
glass transition and softening point), expressed in 1/.degree. C.
(.degree. C..sup.-1), E is the elastic modulus of the glass,
expressed in GPa (not MPa) (which allows values of the
(non-dimensional) parameter .PSI. to range generally between 0 and
1), T.sub.strain is the strain point temperature of the glass, (the
temperature of the glass at a viscosity of .eta.=10.sup.14.7 Poise)
expressed in .degree. C., and T.sub.soft is the softening point of
the glass (the temperature of the glass at a viscosity of
.eta.=10.sup.7.6 Poise), expressed in .degree. C.
The thermal strengthening process and resulting surface compressive
stresses were modeled for glasses having varying properties to
determine the tempering parameter, .PSI.. The glasses were modeled
at the same starting viscosity of 10.sup.8.2 Poise and at varying
heat transfer coefficients. The properties of the various glasses
are shown in Table II, together with the temperature for each glass
at 10.sup.8.2 Poise and the calculated value of the temperability
parameter .PSI. for each.
TABLE-US-00002 TABLE II 10.sup.8.2 CTE CTE Poise Softening Strain
Glass Modulus low high .degree. C. Point .degree. C. Point .degree.
C. .PSI. SLG 72 8.8 27.61 705 728 507 0.76 2 73.3 8.53 20.49 813
837 553 0.77 3 65.5 8.26 26 821 862 549 0.83 4 65 8.69 20.2 864 912
608 0.74 5 63.9 10.61 22 849 884 557 0.84 6 58.26 3.5 20.2 842 876
557 0.49 7 73.6 3.6 13.3 929 963 708 0.44 8 81.1 3.86 12.13 968 995
749 0.48
The results in Table II show that .PSI. is proportional to the
thermal strengthening performance of the glass. This correlation is
further shown in FIG. 11, which provides an embodied example for a
high heat transfer rate (a heat transfer coefficient of 2093
W/m.sup.2K (0.05 cal/scm.sup.2.degree. C.)) and a glass sheet
thickness of only 1 mm. As seen in the figure, the variation in the
seven differing glasses' resulting compressive stress correlates
well with the variation in the proposed temperability parameter
.PSI..
Thermally Tempered Cover Glass Sheet Heat Transfer Coefficient and
Relation to Surface Compressive Stress and Central Tension
Stress
In another aspect, it has been found that for any glass, at any
given value of the heat transfer coefficient, h (expressed in
cal/cm.sup.2-s-.degree. C.), the curves of surface compressive
stress (acs, in MPa) vs. thickness (t, in mm) can be fit (over the
range of t from 0 to 6 mm) by the hyperbola, where P.sub.1 and
P.sub.2 are functions of h such that:
.sigma..function..function..PSI..function..function..function..PSI..funct-
ion. ##EQU00007## or with the expression for .PSI. substituted in,
the curve of compressive stress .sigma..sub.cs(Glass,h,t) is given
by:
.function..function..alpha..alpha. ##EQU00008## where the constants
P.sub.1, P.sub.2, in either (6) or (7) above, are each continuous
functions of the heat transfer value, h, given by:
.times..times. ##EQU00009##
The constants P.sub.1, P.sub.2, are graphed as functions of h in
FIGS. 12 and 13, respectively. Accordingly, by using a value of
P.sub.1, for a given h and the corresponding P.sub.2, for that same
h in expression (6) or (7) above, a curve is specified
corresponding to the surface compressive stress (CS) obtainable at
that h, as a function of thickness t.
In some embodiments, a similar expression may be used to predict
the central tension (CT) of a thermally strengthened cover glass
sheet, particularly at a thickness of 6 mm and less, and the
thermal transfer coefficient, such as 800 W/m.sup.2K and up, by
simply dividing the compressive stress predicted under the same
conductions by 2. Thus, expected central tension may be given
by
.times..function..times..function..alpha..alpha. ##EQU00010## Where
P.sub.1CT and P.sub.2CT are given as follows:
.times..times..times..times. ##EQU00011## In some embodiments, h
and h.sub.CT, may have the same value for a given physical instance
of thermal strengthening. However, in some embodiments, they may
vary, and providing separate variables and allowing variation
between them allows for capturing, within descriptive performance
curves, instances in which the typical ratio of 2:1 CS/CT does not
hold.
One or more embodiments of the currently disclosed processes and
systems have produced thermally strengthened SLG sheets at all of
the heat transfer rate values (h and h.sub.CT) shown in Table
III.
TABLE-US-00003 TABLE III h and h.sub.CT values according to
exemplary embodiments cal/s cm.sup.2 .degree. C. W/m.sup.2K 0.010
418.68 0.013 544.284 0.018 753.624 0.019 795.492 0.020 837.36 0.021
879.228 0.022 921.096 0.023 962.964 0.027 1130.436 0.028 1172.304
0.029 1214.172 0.030 1256.04 0.031 1297.908 0.033 1381.644 0.034
1423.512 0.038 1590.984 0.040 1674.72 0.041 1716.588 0.042 1758.456
0.045 1884.06 0.047 1967.796 0.048 2009.664 0.049 2051.532 0.050
2093.4 0.051 2135.268 0.052 2177.136 0.053 2219.004 0.054 2260.872
0.055 2302.74 0.060 2512.08 0.061 2553.948 0.062 2595.816 0.063
2637.684 0.065 2721.42 0.067 2805.156 0.069 2888.892 0.070 2930.76
0.071 2972.628 0.078 3265.704 0.080 3349.44 0.081 3391.308 0.082
3433.176 0.095 3977.46 0.096 4019.328 0.102 4270.536 0.104 4354.272
0.105 4396.14 0.127 5317.236 0.144 6028.992 0.148 6196.464 0.149
6238.332 0.184 7703.712
In some embodiments, the heat transfer value rates (h and h.sub.CT)
may be from about 0.024 to about 0.15, about 0.026 to about 0.10,
or about 0.026 to about 0.075 cal/scm.sup.2.degree. C.
FIG. 14 shows the newly opened performance space in MPa of surface
compression of a glass sheet as a function of thickness t (in mm),
by a graph of C(h,t).PSI.(SLG) for selected values of h according
to equations 6-9 above, with .PSI.(SLG) corresponding to the value
of .PSI. for SLG in Table II. The traces labeled GC represent the
estimated range of maximum stresses versus thinness of SLG sheets
achievable by gas convective tempering, from 0.02 cal/s
cm.sup.2.degree. C. (or 840 W/m.sup.2K) to 0.03
cal/scm.sup.2.degree. C. or 1250 W/m.sup.2K, assuming that these
levels of heat transfer coefficient can be employed in that process
at a heated glass viscosity of 10.sup.8.2 Poises or about
704.degree. C., a temperature above the capability of convective
gas processes.
Examples of highest reported sheet CS values based on gas
convective tempering processes are shown by the triangle markers
labeled Gas in the legend. The value 601 represents advertised
product performance capability of commercial equipment, while the
value 602 is based on an oral report at a glass processing
conference. The trace labeled LC represents the curve of maximum
stresses versus thinness of SLG sheets estimated to be achievable
by liquid contact tempering, given by a heat transfer rate h of
0.0625 cal/scm.sup.2.degree. C. (or about 2600 W/m.sup.2K), also
assuming processing at an initial heated glass viscosity of
10.sup.8.2 Poises or about 704.degree. C. Examples of highest
reported sheet CS values based on liquid contact tempering
processes are shown by the circle markers labeled Liquid in the
legend. The higher of the two values at 2 mm thickness is based on
a report of tempering of a borosilicate cover glass sheet, and the
stress achieved has been scaled for the figure by
(.PSI..sub.SLG)/(.PSI..sub.borosilicate) for scaled direct
comparison.
The trace labeled 704 represents stresses achievable by one or more
embodiments of the presently disclosed methods and systems at a
heat transfer rate of 0.20 cal/scm.sup.2.degree. C. (or about 8370
W/m.sup.2K) and an initial temperature, just before quenching, of
704.degree. C. The level of stress on the cover glass sheet thus
achievable represents almost the same scope of improvement over
liquid tempering strength levels as liquid tempering represents
over state of the art gas convective tempering. But the trace
labeled 704 is not an upper limit--embodiments have been shown to
be viable above this value due to the good control of form and
flatness achievable in a small-gap gas bearing thermal
strengthening at even higher temperatures (at lower viscosities of
the cover glass). The trace labeled 730 shows some of the
additional strengthening performance achieved by a heat transfer
rate of 0.20 cal/scm.sup.2.degree. C. (or about 8370 W/m.sup.2K) at
a starting temperature for a SLG sheet of 730.degree. C., very near
or above the softening point of the cover glass. Significant
improvements in compressive stress and thus in cover glass sheet
strength are thus achieved particularly by the combination of high
heat transfer rate and the use of high initial temperatures enabled
by the good handling and control of sheet flatness and form in a
tight gas bearing--and the improvements are particularly striking
at thickness 2 mm and below.
FIG. 15 shows the traces of FIG. 14 explained above, at 2 mm and
below, but with compressive stress as a function of thickness
plotted for selected examples of tempered cover glass sheets
produced by one or more embodiments of the present disclosure,
showing the extreme combination of thermal strengthening levels and
thinness enabled by the present disclosure.
Thermally Tempered Cover Glass Sheet with Low Surface Roughness and
High Degree of Flatness
In various embodiments, thermally strengthened cover glass sheets
disclosed herein, such as sheet 500, have both high thermal
stresses and low, as-formed surface roughness. The processes and
methods disclosed herein can thermally strengthen a sheet of cover
glass without increasing the surface roughness of the as-formed
surfaces. For example, incoming float cover glass air-side surfaces
and incoming fusion formed cover glass surfaces were characterized
by atomic force microscopy (AFM) before and after processing.
R.sub.a surface roughness was less than 1 nm (0.6-0.7 nm) for
incoming 1.1 mm soda-lime float cover glass, and the R.sub.a
surface roughness was not increased by thermal strengthening
according to the present processes. Similarly, an R.sub.a surface
roughness of less than 0.3 nm (0.2-0.3) for 1.1 mm sheets of
fusion-formed cover glass was maintained by thermal strengthening
according to this disclosure. Accordingly, thermally strengthened
cover glass sheets have a surface roughness on at least a first
surface in the range from 0.2 to 1.5 nm R.sub.a roughness, 0.2 to
2.0 nm R.sub.a roughness, 0.2 to 0.7 nm, 0.2 to 0.4 nm or even such
as 0.2 to 0.3 nm, over at least an area of 10.times.10 .mu.m.
Surface roughness may be measured over an area of 10.times.10 .mu.m
in exemplary embodiments, or in some embodiments, 15.times.15
.mu.m.
In some contemplated embodiments, thermally strengthened cover
glass sheets disclosed herein have both high thermal stresses and
low, as-formed surface roughness and/or coated surfaces. The
processes and methods disclosed herein can thermally strengthen a
sheet of cover glass without increasing the surface roughness of
smooth as-formed or as-delivered surfaces of cover glass sheets,
and likewise without damaging sensitive low-E or anti-reflective or
other coatings. Incoming float cover glass air-side surfaces, and
incoming fusion-formed cover glass surfaces, were characterized by
atomic force microscopy (AFM) before and after processing. R.sub.a
surface roughness was less than 1 nm (such as 0.6 to 0.7 nm) for
incoming on the air side of 1.1 mm soda-lime float cover glass and
was not increased by thermal strengthening according to the present
disclosure. R.sub.a surface roughness was less than 0.3 nm (such as
0.2 to 0.3 nm) incoming on 1.1 mm sheets of fusion-formed cover
glass and likewise was not increased by thermal strengthening
according to this disclosure. Accordingly, in contemplated
embodiments, thermally strengthened cover glass sheets, according
to this disclosure, have surface roughness on at least a first
surface in the range of at least 0.2 nm and/or no more than 1.5 nm
R.sub.a roughness, such as no more than 0.7 nm, such as no more
than 0.4 nm or even such as no more than 0.3 nm, or have thermally
strengthened sheets having coatings thereon of the type that may be
applied before strengthening, or have combinations of these low
roughness values and coatings, are obtained from the present
process used with corresponding cover glass sheets as starting
material. It is Applicant's understanding that such preservation of
surface quality and/or surface coating(s) previously required use
of convective gas tempering or perhaps a low heat transfer liquid
tempering process, which produces limited thermal strengthening
effects relative to the total range available with the present
processes and methods.
In another embodiment, the thermally strengthened cover glass
sheets described herein have high flatness. In various embodiments,
the strengthening system discussed herein utilizes controlled gas
bearings to support the glass material during transporting and
heating, and in some embodiments, can be used to assist in
controlling and/or improving the flatness of the cover glass sheet,
resulting in a higher degree of flatness than previously
obtainable, particularly for thin and/or highly strengthened cover
glass sheets. For example, sheets at least 0.6 mm can be
strengthened with improved post-strengthening flatness. The
flatness of thermally strengthened cover glass sheets embodied
herein can comprise 100 .mu.m or less total indicator run-out (TIR)
along any 50 mm length along one of the first or second surfaces
thereof, 300 .mu.m TIR or less within a 50 mm length on one of the
first or second surfaces, 200 .mu.m TIR or less, 100 .mu.m TIR or
less, or 70 .mu.m TIR or less within a 50 mm length on one of the
first or second surfaces. In exemplary embodiments, flatness is
measured along any 50 mm or less profile of the glass sheet. In
contemplated embodiments, sheets with thickness disclosed herein
have flatness 200 .mu.m TIR or less within a 20 mm length on one of
the first or second surfaces, such as flatness 100 .mu.m TIR or
less, flatness 70 .mu.m TIR or less, flatness 50 .mu.m TIR or
less.
According to contemplated embodiments, the strengthened cover glass
or glass-ceramic articles discussed herein (e.g., cover glass sheet
500 shown in FIG. 4) have a high-degree of dimensional consistency
such that the thickness t thereof along a 1 cm lengthwise stretch
of the body 522 does not change by more than 50 .mu.m, such as, by
not more than 10 .mu.m, not more than 5 .mu.m, not more than 2
.mu.m. Such dimensional consistency may not be achievable for given
thicknesses, areas, and/or magnitudes of negative tensile stress,
as disclosed herein, by solid quenching due to practical
considerations, such as cooling plate alignment and/or surface
irregularities that may distort the dimensions.
According to contemplated embodiments, the strengthened cover glass
or glass-ceramic articles discussed herein have at least one major
surface (e.g., first and second surfaces 510, 520 of the
strengthened cover glass or glass-ceramic sheet 500 in FIG. 4) that
is flat such that a 1 cm lengthwise profile therealong stays within
50 .mu.m of a straight line, such as within 20 .mu.m, 10 .mu.m, 5
.mu.m, 2 .mu.m; and/or a 1 cm widthwise profile therealong stays
within 50 .mu.m of a straight line, such as within 20 .mu.m, 10
.mu.m, 5 .mu.m, 2 .mu.m. Such high flatness may not be achievable
for given thicknesses, areas, and/or magnitudes of negative tensile
stress, as disclosed herein, by liquid quenching due to practical
considerations, such as warping or bending of the cover glass
strengthened in these processes due to convective currents and
associated forces of the liquid.
Thermally Strengthened Cover Glass Sheet CTE
Another aspect comprises thermally strengthened low coefficient of
thermal expansion (CTE) cover glass sheets. As discussed above (see
e.g., equations 7 and 10), thermal strengthening effects are
significantly dependent upon the CTE of the glass of which the
cover glass sheet is comprised. However, thermal strengthening of
low CTE glasses may provide strengthened glass compositions having
advantageous properties, such as increased chemical resistance, or
better compatibility with electronic devices due to low alkali
content. Cover glass sheets having CTEs of 65, 60, 55, 50, 45, 40,
and even 35.times.10.sup.-6.degree. C..sup.-1 and below are capable
of safety-glass like break patterns ("dicing") at thicknesses of
less than 4 mm, less than 3.5 mm, less than 3 mm, and even at 2 mm
or less. Cover glasses having CTE values of
40.times.10.sup.-6.degree. C..sup.-1 and below can be strengthened
using the processes described herein. Such low CTE glasses
strengthened by the systems and methods discussed herein can have
similar surface compressions to SLG sheets strengthened by
convention commercial (gas convective) processes at the same
thickness. In some embodiments, the compressive stress of low CTE
glasses can comprise at least 50 MPa, at least 100 MPa, at least
125 MPa, at least 150 MPa, at least 200 MPa, at least 250 MPa, at
least 300 MPa, or at least 400 MPa for cover glass sheets having a
thickness of no more than 1 cm, no more than 5 mm, no more than 3
mm, no more 2 mm, no more than 1.5 mm, no more than 1 mm, no more
than 0.75 mm, no more than 0.5 mm, no more than 0.3 mm, no more
than 0.2 mm, or no more than 0.1 mm.
Cover glass sheets formed according to the present disclosure have
a multitude of applications in consumer electronic devices, for
example in electronic devices, mobile phones, portable media
players, televisions, notebook computers, watches, household
appliances, tablet computer displays and in laminates, such as
glass-interlayer-glass laminates used in various consumer
electronic devices. Stronger and thinner laminates can be produced,
resulting in weight and cost savings and fuel efficiency increases.
Desirably, a thermally strengthened thin sheet may be cold bent and
laminated to a formed thicker glass, providing an easy and reliable
manufacturing process not requiring any hot forming of the thin
sheet.
Alpha of Thermally Tempered Cover Glass Sheet
Table IV below shows results obtained by the methods of the present
disclosure (indicated as "Source of Method" I in the table), and a
figure of merit, Alpha, that is a rough measure of the coefficient
of heat exchange obtained within the tempering process. Alpha is
given by:
##EQU00012## where CS is physical compressive stress (in MPa), t is
thickness in millimeters, CTE is the coefficient of thermal
expansion in .degree. C..sup.-1, and E is the elasticity of the
glass in (MPa), and yields units in .degree. C./mm.
TABLE-US-00004 TABLE IV Sample Source of Thickness Alpha No. Method
Glass (mm) CS (MPa) CTE (1/C) E (MPa)** (C/mm) 1 I SLG 1.84 150
9.20E-06 68900 129 2 I SLG 1.84 172 9.20E-06 68900 147 3 I SLG 1.07
190 9.20E-06 68900 280
Samples 1 and 3 are repeatable values obtained from the disclosed
processes, sample 1 using air and sample 3 using helium as the gas
in the process. Sample 2 represents a "champion" value using air
within the present process, that is, not reliably repeatable to
date. Cover glass samples processed by the processes of the present
disclosure (samples 1-3) all exceeded an Alpha at 117.degree.
C./mm. Applicant believes that the slope of Alpha with thickness
may have an inherent trend lower with lower glass thickness. Glass
disclosed herein has an Alpha of greater than 20t+77, where t is
thickness of the cover glass, in mm, in some embodiments.
Thermal Strengthening System and Process
In various embodiments, a process for strengthening a cover glass
sheet comprises supporting or guiding at least a portion of a cover
glass sheet, such as cover glass sheet 500, into a cool or
quenching zone in which the sheet is rapidly cooled creating a
strengthened cover glass sheet having one or more of the properties
discussed herein. In various embodiments, the cover glass sheet is
supported at least in part by a flow or a pressure of a gas
delivered to a gap between the surfaces of the cover glass sheet
and one or more heat sinks. In general, the temperature of the
glass sheet is above the transition temperature of the glass when
the sheet is moved into the cool zone, and in various embodiments,
the cover glass sheet is cooled within the cooling zone by thermal
conduction more than by convection. Conduction is a process of heat
transfer where energy is transmitted through interactions between
adjacent molecules, and convection is a process of heat transfer
where energy is communicated via motion of a fluid (e.g., air,
helium, etc.), such as where heated fluid moves away from a heat
source and is replaced by cooler fluid. Thus, the present system is
markedly different from conventional convection-based glass
strengthening/tempering systems in which the primary mode of heat
transfer during cooling of the glass sheet is convective.
In some embodiments, an overall process for strengthening a cover
glass sheet comprises heating a cover glass sheet in a hot zone and
then cooling the cover glass sheet in a cooling zone. The cover
glass sheet has a transition temperature, which is the temperature
at which the viscosity of the cover glass has a value of
i=10.sup.12-10.sup.13.3 Poise. The cover glass is heated
sufficiently to bring the cover glass sheet above the transition
temperature, and then moved into a cooling zone. Optionally, the
cover glass can be transitioned from the hot zone to a cool zone
through a transition zone. In the cooling zone, the surfaces of the
cover glass sheet are positioned adjacent to heat sinks, one on
either side of the cover glass sheet, each with a gap in between
one of the cover glass surfaces and an opposing surface of the heat
sink. Gas is delivered into the gaps through multiple apertures in
the heat sinks, and in some embodiments, this delivered gas forms
an air bearing which supports the cover glass between the heat
sinks such that the cover glass surfaces are not in contact with
the heat sinks. Within the cooling zone, the cover glass sheet is
cooled by conduction more than by convection and is cooled
sufficiently to fix or create a thermally induced surface
compression and a thermally induced central tension of the sheet
which provides the increased strength as discussed herein. In
various embodiments, primarily cooling via conduction is achieved
by having a very low gap size within the cooling zone such that the
cover glass sheet is close to, but not touching, the opposing
surfaces of the heat sinks.
An apparatus for enabling the processes described can include a
heating zone for heating a cover glass sheet to a temperature above
the transition temperature and a cooling zone for cooling the
heated cover glass sheet to provide a strengthened cover glass
sheet. The apparatus can include an optional transition zone
between the heating zone and the cooling zone. The cooling zone may
include a heat sink having a pair of opposing surfaces defining a
gap, within which the heated cover glass sheet is received. The
cooling zone can comprise a pair of gas bearings disposed on
opposite sides of that gap that acts to support the cover glass
sheet within the gap. The gap can be configured to cool the heated
cover glass sheet by conduction more than by convection. In some
embodiments, the gas bearings can include a plurality of apertures
for delivering the gas to the gap, and the gas bearing surfaces act
as the heat sinks, capable of conducting heat away from the heated
cover glass sheet by conduction more than by convection.
Strengthening processes and equipment disclosed herein (see
generally FIGS. 21-25) allow for strengthening of cover glass or
glass-ceramic articles (see generally FIGS. 4-7 and 27-30) by an
inventive form of thermal tempering. The processes allow for steep,
tensile stress versus thickness/depth curves (see generally FIG.
6), particularly steep in slope near the surface of the cover glass
or glass-ceramic articles, which enable strengthening of the cover
glass or glass ceramic articles to particularly high levels of
negative tensile stress for a given thickness near the surface of
the respective articles, without requiring strengthening by
ion-exchange or laminating different glasses. However, in some
embodiments, the thermal tempering processes disclosed herein may
be augmented with ion-exchange or applied to glass-to-glass
laminations. The thermal tempering processes disclosed herein
enable particularly high levels of strengthening in large-area
articles (e.g., sheets) that may be too large for strengthening via
conventional thermal tempering methods, such as due to alignment
limitations of contact quench equipment, cooling rate limitations
of conventional convection systems, and/or warping damage
associated with liquid quench tempering. The processes disclosed
herein uniquely allow high levels of strengthening in particularly
thin sheets that may be too thin for strengthening via conventional
tempering methods, such as due sensitivity to breakage or fracture
of the thin cover glass or glass ceramic articles during the
strengthening process and associated contact forces with solid or
liquid quenching and/or due to the cooling rate limitations of
conventional convection tempering. However, in other contemplated
embodiments, cover glass or glass ceramic articles as disclosed
herein may be manufactured with at least some solid or liquid
quenching, such as in combination with the unique strengthening
processes disclosed herein.
One embodiment of a method according to this disclosure is
illustrated in the flow chart of FIG. 16. The method or process 100
includes a step 140 of providing a cover glass sheet that is at a
temperature above a transition temperature of the glass sheet. The
method or process 100 also includes the step 160 of supporting a
cover glass sheet at least in part by a gas (through gas flow and
pressure). Step 160 includes, while the cover glass sheet is
support by the gas, cooling the sheet: 1) by conduction more than
by convection through the gas to a heat sink, and 2) sufficiently
to create or fix a thermally-induced surface compression stress and
a thermally-induced central tension stress, of the sheet when at
ambient temperature.
According to a variation on the embodiment of FIG. 16, depicted as
method 100' in the flow chart of FIG. 17, the method can include
the step 110 of heating a cover glass sheet sufficiently such that
the sheet is above a transition temperature of the glass. As part
of, or as preparation for, the cooling step 160, the method 100'
further comprises, in step 120, providing a heat sink (whether as a
single piece or in separate pieces) having first and second heat
sink surfaces (see generally FIGS. 21-25), each having apertures
therein. In step 130A the method further includes positioning a
first sheet surface facing a first heat sink surface across a first
gap and, in step 130B, positioning the second sheet surface facing
a second heat sink surface across a second gap. The heat sink
surfaces can include apertures and/or can be porous. The method
100' can further include, in step 160, cooling the sheet, by
conduction more than by convection through a gas to the respective
heat sink surfaces, sufficiently to strengthen the cover glass
(e.g., to sufficiently create or fix in the sheet a
thermally-induced surface compression stress and a
thermally-induced central tension stress). The step 160 also can
include delivering the gas to the first and second gaps through the
apertures or porous heat sink, and in some such embodiments, the
gas is delivered to form air bearings that support the cover glass
sheet adjacent the heat sinks. In some embodiments, the gas is
delivered only through the apertures of the heat sink or only
through the pores or pores and apertures of the porous heat
sink.
These and other related methods of this disclosure go against the
currently dominant technique of gas-convection-cooling by using
conduction as the dominant mode of cooling, instead of convection.
Instead of a solid-to-gas (glass to air) heat exchange, methods
described herein use a solid-to-solid (glass to heat sink) heat
exchange, mediated across a small gap by a small amount of gas
(e.g., without physical contact between glass surfaces and heat
sink), both to begin and to complete the cooling that produces
thermal strengthening. Although some convection is present as gas
(e.g., air bearing gas) flows into the small gap, conduction
directly across the gap through the gas and into the heat sink is
the principal mode of cooling. Applicant has determined that
dominance of conductive heat transfer increases the rate of heat
transfer relative to convection dominant cooling processes.
Because solid-to-solid conduction (even across the gap) allows for
more rapid heat flow than convection, the cooling rate increases
needed for thinner cover glass sheets are not tied to gas velocity
and volume. According to various embodiments, without the
constraints typically imposed by gas flow and gap size in a
convective system, gas flow and gap size can be selected,
controlled or optimized for other purposes, such as for controlling
stiffness of the gas cushion in the gap, for supporting the sheet,
for flattening or otherwise shaping a sheet, for optimizing heat
conduction, for maintaining sheet flatness and/or shape during
thermal strengthening, and/or for balancing ease of sheet handling
with high cooling rates. For example, in some embodiments, because
cooling is not via convection, helium becomes an economically
viable alternative to air in the system of the present disclosure
due to the very low gas flow rates that support the gas bearing,
and in such embodiments, helium offers thermal conductivity about
five times that of air. Even helium with prices assumed at
multiples of those available today becomes an economically viable
alternative at the low flow rates of the system of the present
disclosure.
Further, because the system of the present disclosure decreases the
volume of air flowing over a cover glass sheet during cooling
(relative to convective systems), the systems and methods discussed
herein decrease the potential risk of deformation of hot thin
sheets of cover glass typically caused by the high speed, high
volume air flows needed in conventional convection based tempering
systems. This also allows softer, higher temperature cover glass
sheets to be handled with no or minimal distortion, further
improving the achievable degree of strengthening. Eliminating high
air flow rates also eases problems sometimes seen in transporting
the sheet into the quenching chamber (moving against the high air
flow) and in keeping the high-flow, cooler air from entering into
and cooling the adjacent parts of the furnace used to heat the
sheet.
Further the use of conduction, through a gas, may mitigate contact
damage, warping, shaping, etc. associated with conventional liquid
contact or solid contact quench tempering. Use of a gas as an
intermediate conductor preserves the surface quality of the
processed articles by avoiding solid-to-solid contact. Mediating
the high conduction rates through a gas also avoids liquid contact.
Some types of liquid quenching can introduce unwanted distortions,
spatial variation in tempering and contamination of the cover glass
surfaces. These embodiments essentially provide non-contact (except
by a gas) but very high-rate cooling. In other embodiments, as
discussed above, solid- or liquid-contact may be included.
Power Consumption of Thermal Tempering System/Process
Another advantage of avoiding high air flow rates lies in the power
and energy savings achieved by using solid-gas-solid conduction as
the primary cover glass cooling mechanism. Points A and B of FIG.
18 and FIG. 19 represent a high-end estimate of peak power use of
the air bearing, per square meter of cover glass sheet, by a
compressed air supply at relatively high flow. Practical low-end
peak power use of compressed air could be as little as 1/16 of the
values shown. Points A and B do not include active cooling of the
heat sink, however, which can be included in some embodiments,
especially where .alpha. machine is in continuous, quasi-continuous
or high frequency operation.
Referring again to FIG. 18 and FIG. 19, points A' and B' represent
the conservatively estimated peak power levels for operation of the
air bearing at points A and B when active cooling of the heat sink
surfaces is factored in, assuming the thermal load equivalent of a
300.degree. C. drop in cover glass sheet temperature is
accomplished by an active cooling system having a
thermal-to-mechanical (or electrical) efficiency ratio of 7.5 to 1,
within a time limit of 2.1 seconds for point A' and within 1 second
for point B'. (These points correspond approximately to cover glass
sheets actually tempered in the apparatus described herein.)
Although the four points within region R of FIG. 18 and FIG. 19
illustrate the significance of the improvement obtainable by the
methods and systems of the present disclosure (at least to some
degree), it should be noted that the full benefits are likely
significantly understated in the figures because power demand is
the quantity represented. For example, peak power of air blowers,
as represented by the curve N, is not efficiently turned on and
off, typically requiring gated airways to block off large fans,
which still rotate (but at reduced load), when air is not needed.
Peak power demands of fluid cooling systems such as chilled water
plants, represented by the points A' and B' as examples easily
achievable according to the present disclosure, can generally be
much more efficiently accommodated, and effective peak power would
be significantly lower, approaching A' and B' only as fully
continuous operation is approached. Thus, the difference in total
energy demands would tend to be greater than the difference for
peak power demand, which is represented in the figure. In some
embodiments, the processes described herein have peak powers of
less than 120 KW/m.sup.2, less than 100 KW/m.sup.2, less than 80
KW/m.sup.2 to thermally strengthen a cover glass sheet of 2 mm
thickness or less.
Heat Transfer from Thin Cover Glass Sheet During Thermal
Tempering
In general, heat transfer from the thin cover glass sheet in the
system and process of the present disclosure includes a conduction
component, a convection component and a radiant component. As noted
above and explained in detail herein, the thermal tempering system
of the present disclosure provides for thin cover glass tempering
by utilizing conductive heat transfer as the primary mechanism for
quenching the thin cover glass sheets.
The following is Applicant's understanding of the underlying
theory. It may well occur to one of ordinary skill in the art of
glass tempering, in which conduction effects are normally so small
as to be commonly ignored in favor of analysis of convection and
radiation alone, to ask whether sufficiently high cooling rates for
thin cover glass sheets (such as at 2 millimeters and below) are
actually achievable by conduction through a gas such as air--and if
so, whether such rates are achievable at practical gap sizes.
The amount of thermal conduction at conditions embodied in
processes using systems described herein can be determined via the
following. First, in the context of thermal strengthening by
conduction as in the present disclosure, the thermal conductivity
of the gas within the gap must be evaluated in the direction of
conduction, which is along a thermal slope. Air at high
temperature, at or near the surface of the sheet being cooled, has
significantly higher thermal conductivity than air at a lower
temperature, such as air at or near room temperature at or near the
surface of the heat sink (the nominal thermal conductivity of (dry)
room temperature air (25.degree. C.) is approximately 0.026 W/m-K).
An approximation that assumes air over the whole gap to be at the
average temperature of the two facing surfaces at the start of
cooling is used. At the start of cooling, a cover glass sheet may
be at a temperature of 670.degree. C., for example, while the heat
sink surface may start at 30.degree. C., for example. Accordingly,
the average temperature of the air in the gap would be 350.degree.
C., at which dry air has a thermal conductivity of about 0.047
W/m-K; more than 75% higher than its thermal conductivity at room
temperature and sufficiently high to conduct large amounts of heat
energy through gaps of the sizes within the system of the present
disclosure, as discussed below, assuming the sheet is finished to a
reasonably high degree of surface and thickness consistency.
To illustrate, Q.sub.cond, the conductive component of the rate of
heat transfer through a gap of distance g which gap has an area
A.sub.g (in a direction everywhere perpendicular to the direction
of the gap distance g) may be given by:
.times..function. ##EQU00013## where k is the thermal conductivity
of the material (gas) in the gap evaluated in the direction of (or
opposite of) heat conduction, Ts is the temperature of the cover
glass surface and T.sub.HS is the temperature of the heat sink
surface (or the heat source surface, for other embodiments). As
mentioned above, to evaluate k rigorously would require integrating
the thermal conductivity of the gas along (or against) the
direction of conductive heat flow, as the thermal conductivity of
the gas varies with temperature--but as a good approximation, k may
be taken as the value of k for the gas in the gap when at the
average of the temperatures of the two surfaces, Ts and
T.sub.HS.
Reframing equation (14) in units of heat transfer coefficient
(units of heat flow power per meter squared per degree Kelvin)
gives:
.function. ##EQU00014## so the effective heat transfer coefficient
for conduction across the gap is the thermal conductivity of the
medium in the gap (air in this case) (in units of W/mK) divided by
the length of the gap (in meters), giving a value of Watts per
meter squared per degree of temperature difference. Table V shows
the heat transfer coefficients (k/g), due to conduction alone, for
air and helium filled gaps of gap sizes from 10 .mu.m up to 200
.mu.m in steps of 10 .mu.m each.
TABLE-US-00005 TABLE V Air Helium conductivity (W/m/K) 0.047
conductivity (W/m/K) 0.253 heat trans coeff. heat trans coeff. Gap
(m) W/m.sup.2/K cal/s/cm.sup.2 Gap (m) W/m.sup.2/K cal/s/cm.sup.2
0.00001 4700 0.11226 0.00001 25300 0.604291 0.00002 2350 0.05613
0.00002 12650 0.302145 0.00003 1566.67 0.03742 0.00003 8433.33
0.20143 0.00004 1175 0.028065 0.00004 6325 0.151073 0.00005 940
0.022452 0.00005 5060 0.120858 0.00006 783.333 0.01871 0.00006
4216.67 0.100715 0.00007 671.429 0.016037 0.00007 3614.29 0.086327
0.00008 587.5 0.014032 0.00008 3162.5 0.075536 0.00009 522.222
0.012473 0.00009 2811.11 0.067143 0.0001 470 0.011226 0.0001 2530
0.060429 0.00011 427.273 0.010205 0.00011 2300 0.054936 0.00012
391.667 0.009355 0.00012 2108.33 0.050358 0.00013 361.538 0.008635
0.00013 1946.15 0.046484 0.00014 335.714 0.008019 0.00014 1807.14
0.043164 0.00015 313.333 0.007484 0.00015 1686.67 0.040286 0.00016
293.75 0.007016 0.00016 1581.25 0.037768 0.00017 276.471 0.006604
0.00017 1488.24 0.035547 0.00018 261.111 0.006237 0.00018 1405.56
0.033572 0.00019 247.368 0.005908 0.00019 1331.58 0.031805 0.0002
235 0.005613 0.0002 1265 0.030215
FIG. 20 (Prior Art) shows an industry-standard curve from about 35
years ago (with reference line at 2 mm added) showing the heat
transfer coefficient required to fully temper a sheet of glass, as
a function of thickness in mm, under certain assumed conditions. As
may be seen from a comparison of Table V with FIG. 20, an
air-filled gap of approximately 40 .mu.m can allow full tempering
of 2 mm thick cover glass by conduction. While slightly less than
40 micrometers is a rather small gap, planar porous air bearings in
conveyor applications may generally be reliably run with gaps of as
low as 20 micrometers. Thus 37 micrometers is achievable for an air
gap fed by pores in the heat sink surface. Using helium (or
hydrogen, with similar thermal conductivity) as the gas, a gap of
about 200 .mu.m can be used to fully temper 2 mm thick cover glass.
Using helium or hydrogen as the gas allows for a gap size about 5
times larger for the same heat transfer coefficient. In other
words, using helium or hydrogen as the gas in the gap increases the
heat transfer coefficient available for quenching by about 5 times
at the same gap size. So even with air the spacing is not
impractical, and with high conductivity gases, the gap spacing is
relatively easy to achieve, even for sheet thicknesses smaller than
2 millimeters.
In addition to cooling through a gas by conduction more than by
convection, another embodiment includes heating (or heating and/or
cooling) through a gas by conduction more than by convection.
Regarding the relative contributions of conduction and convection,
whether for heating or cooling, the convective Q.sub.conv component
of the rate of heat transfer across the gap (or gaps) may be given
by:
.times..times..times..function. ##EQU00015## where in is the mass
flow rate of the gas, Cp is the specific heat capacity of the gas,
T, is the inlet temperature of the gas as it flows into the gap,
and e is the effectiveness of the heat exchange between the gas
flowing in the gap, the sheet surface and the surface of the heat
sink/source (the "walls" of the gap). The value of e varies from 0
(representing zero surface-to-gas heat exchange) to 1 (representing
the gas fully reaching the temperature of the surfaces). The value
of e can be computed by those skilled in the art of heat transfer
using, for example, the e-NTU method.
Typically, however, if the gap between the surface of the sheet and
the surface of the heat sink/source is small, the value of e will
be very nearly equal to 1, meaning the gas heats nearly
completely--to equal, on average, the average of the temperatures
of the two surfaces on either side--before it leaves the gap.
Assuming e=1 (a slight overestimate of the rate of convective heat
transfer), and the gas being supplied to the gap through the
surface of the heat sink/source, it can be assumed that the initial
temperature of the gas in the gap is the same as the temperature of
the surface of the heat sink/source (T.sub.i=T.sub.HS). The rate of
heat transfer due to convection may then be simplified to:
.times..function..times. ##EQU00016##
At the temperatures typically useful for heat strengthening or heat
treating of glass and similar materials, radiative heat transfer
out of the sheet under treatment is relatively small. To cool (or
heat, assuming the amount of radiation from the heat source when
heating is not too high) the sheet (e.g., sheet 200 shown in FIG.
21) principally by conduction, in the area of the gap (e.g., gaps
204a, 204b shown in FIG. 21), thus requires only that:
Q.sub.cond>Q.sub.conv (18) Combining (18) with equations (14)
and (17) gives the following conditional:
>.times..times. ##EQU00017## which, when held, will essentially
ensure that the sheet, in the area of the gap at issue, is cooled
(or heated) principally by conduction. Accordingly, the mass flow
rate {dot over (m)} of the gas should be less than
2kA.sub.g/gC.sub.p, or 2k/gC.sub.p per square meter of gap area. In
an embodiment, {dot over (m)}<B(2kA.sub.g/gC.sub.p), where B is
the ratio of convective cooling to conductive cooling. As used
herein, B is a positive constant less than one and greater than
zero, specifically having a value of 2/3 or less, or even 4/5 or
9/10 or less. Generally, {dot over (m)} should be kept as low as
possible, consistent with the needs of using the gas flow to
control the position of the cover glass sheet (e.g., sheet 200
shown in FIG. 21 relative to the heat sink surface(s)) (e.g., heat
sink surfaces 201b, 202b, shown in FIG. 21) or the position of the
heat exchange surfaces themselves. The ratio of convective cooling
to conductive cooling can be any value from less than one to
1.times.10.sup.-8. In some embodiments, B is less than 0.9, 0.8,
0.7, 0.6, 0.5, 0.4, 0.1, 5.times.10.sup.-2, 1.times.10.sup.-2,
5.times.10.sup.-3, 1.times.10.sup.-3, 5.times.10.sup.-4,
1.times.10.sup.-4, 5.times.10.sup.-5, 1.times.10.sup.-5,
5.times.10.sup.-6, 1.times.10.sup.-6, 5.times.10.sup.-7,
1.times.10.sup.7, 5.times.10.sup.8, or 1.times.10.sup.8. In some
embodiments, {dot over (m)} is minimized, consistent with the needs
of using the gas flow to support and control the sheet position
relative to the heat sink surface(s). In other embodiments, m
should be selected to control the position of the heat exchange
surfaces themselves, relative to the sheet.
In various embodiments, the mass flow rate {dot over (m)} of the
gas within the conductive-based cooling system of the present
disclosure is substantially lower as compared to the conventional
convection-based tempering systems. This substantially lower gas
flow rate allows the conductive system to be operated at
substantially reduced power usage, as discussed herein. Further, in
at least some embodiments, the reduced gas flow rate also results
in a substantially quieter cooling system as compared to a
conventional convective cooling system. In such embodiments, the
decrease in noise may increase operator safety by reducing the
potential for hearing damage and even reducing or eliminating the
need for operators to use hearing protection.
As will be understood, in embodiments in which a sheet of cover
glass material is supported on air bearings between opposing heat
sink surfaces, conductive heat transfer will occur from both sides
of the cover glass sheet to both heat sink surfaces Thus, in such
embodiments, the cover glass sheet has first and second sheet
surfaces, and cooling of the cover glass sheet is performed by
positioning the first sheet surface (e.g., a lower surface of the
cover glass sheet) adjacent to a first heat sink surface (e.g., a
surface of a lower heat sink) such that a first gap is located
between the first sheet surface and the first heat sink surface and
by positioning the second sheet surface (e.g., an upper surface of
the cover glass sheet) adjacent to a second heat sink surface
(e.g., a surface of an upper heat sink) such that a second gap is
located between the second sheet surface and the second heat sink
surface. In such embodiments, thermal conduction from the first
sheet surface to the first heat sink surface and from the second
sheet surface to the second heat sink surface is permitted to
occur. In such embodiments, the first gap has a length across the
first gap of g.sub.1 and an area of the first gap of A.sub.g1, and
the second gap has a length across the second gap of g.sub.2 and an
area of the second gap of A.sub.g2. In such embodiments, a first
flow of a first gas to the first gap is provided, and a second flow
of a second gas to the second gap is provided. As will be
understood, similar to the discussion above, the first gas has a
heat capacity C.sub.p1 and a thermal conductivity k.sub.1, and the
first flow is provided at a mass flow rate {dot over (m)}.sub.1. In
such embodiments, m.sub.1 is greater than zero and less than
(2k.sub.1A.sub.g1)/(g.sub.1C.sub.p1). Further, the second gas has a
heat capacity C.sub.p2 and a thermal conductivity k.sub.2, and the
second flow is provided at a mass flow rate {dot over (m)}.sub.2.
In such embodiments, m.sub.2 is greater than zero and less than
(2k.sub.2A.sub.g2)/(g.sub.2Cp.sub.2). In such embodiments, the
first and second flows contact the cover glass sheet such that the
cover glass sheet is supported without touching the heat sink
surfaces. In this manner, the sheet is cooled by conduction more
than by convection in a manner to create a surface compressive
stress and a central tension of the sheet.
Cover Glass Strengthening System Including High Conduction Cooling
Zone
Referring to FIG. 21, a diagrammatic cross-section of a high
conduction glass cooling/quenching station and of a glass sheet
being cooled by conduction more than by convection is shown. A hot
glass sheet 200 has its first and second (major) surfaces 200a,
200b each facing a respective first and second surface 201b, 202b
of respective first and second heat sinks 201a, 202a across
respective gaps 204a and 204b. Gas 230 is fed through the first and
second surfaces 201b, 202b as represented by the arrows, to supply
the gaps 204a, 204b, and to assist in keeping the cover glass sheet
centered or otherwise positioned between the heat sinks 201a, 202a.
The air or other gas may leave passing by the edges of the heat
sinks 201a, 202a as shown by arrows 240. By choosing the size of
the gaps 204a, 204b and the gas and the flow rate of the gas 230 in
accordance with the discussion herein, the cover glass sheet 200
will be cooled more by conduction than convection. In specific
embodiments, cover glass sheet 200 is cooled by heat sinks 201a and
202a such that more than 20%, specifically more than 50%, and more
specifically more than 80%, of the thermal energy leaving a heated
article, such as cover glass sheet 200, crosses the gaps, such as
gaps 204a and 204b, and is received by the heat sink 201a and
202a.
In some embodiments, the gaps 204a, 204b are configured to have a
thickness or distance across the gap sufficient such that the
heated cover glass sheet is cooled by conduction more than by
convention. As will be understood, size of gaps 204a, 204b
generally is the distance between the major cover glass surfaces
and the opposing heat sink surfaces.
In some embodiments, gaps 204a and 204b may have a thicknesses of
about (e.g., plus or minus 1%) 100 .mu.m or greater (e.g., in the
ranges from about 100 .mu.m to about 200 .mu.m, from about 100
.mu.m to about 190 .mu.m, from about 100 .mu.m to about 180 .mu.m,
from about 100 .mu.m to about 170 .mu.m, from about 100 .mu.m to
about 160 .mu.m, from about 100 .mu.m to about 150 .mu.m, from
about 110 .mu.m to about 200 .mu.m, from about 120 .mu.m to about
200 .mu.m, from about 130 .mu.m to about 200 .mu.m, or from about
140 .mu.m to about 200 .mu.m). In other embodiments, gaps 204a and
204b may have a thicknesses of about (e.g., plus or minus 1%) 100
.mu.m or less (e.g., in the ranges from about 10 .mu.m to about 100
.mu.m, from about 20 .mu.m to about 100 .mu.m, from about 30 .mu.m
to about 100 .mu.m, from about 40 .mu.m to about 100 .mu.m, from
about 10 .mu.m to about 90 .mu.m, from about 10 .mu.m to about 80
.mu.m, from about 10 .mu.m to about 70 .mu.m, from about 10 .mu.m
to about 60 .mu.m, or from about 10 .mu.m to about 50 .mu.m).
Heat sinks 201a, 202a may be solid or porous configurations.
Suitable materials include, but are not limited to, aluminum,
bronze, carbon or graphite, stainless steel, etc. Heat sink
dimensions may be designed to be sufficient to address the size of
the cover glass sheet and to efficiently and effectively transfer
heat without changing the heat sink temperature significantly. In
the case where heat sinks 201a and/or 202a are porous, they may
still include additional apertures or holes for flowing gas or may
use the porous structure to provide flow, or both. In some
embodiments, the heat sinks further comprise passages to allow
fluid flow for controlling the temperature of the heat sink,
described in more detail in FIGS. 23-25 and below.
Eliminating high gas flow rates of the prior art may enable use of
very small apertures or pores 206, as shown in FIG. 21, in the heat
sink face to provide the gas to the gap(s). In some embodiments,
apertures may be less than 2 mm, less than 1.5 mm, less than 1 mm,
less than 0.5 mm, less than 0.25 mm, or less than or equal to 200,
150, 100, 50, 30, 20, or 10 .mu.m, when measured in the smallest
direction (e.g., diameter in the case of circular apertures). In
some embodiments, the apertures are from about (e.g., plus or minus
1%) 10 .mu.m to about 1 mm, about 20 .mu.m to about 1 mm, or about
50 .mu.m to about 1 mm.
Spacing between adjacent apertures 206 can be from about (e.g.,
plus or minus 1%) 10 .mu.m to about 3 mm, about 20 .mu.m to about 2
mm, or about 50 .mu.m to about 1 mm, measured edge-to-edge of
apertures. Small apertures or pores may function as individual flow
restrictors, providing high-performance, gas-bearing-type dynamics,
such as high levels of stiffness and consistency of support of the
sheet to position the sheet and control gap size, allowing for high
homogeneity of thermal strengthening effects to avoid or reduce
stress birefringence. Further, because very small pores or
apertures may be used, the relative amount of solid matter at the
surface of the heat sink facing the sheet surface across the gap(s)
can be maximized, thereby increasing conductive heat flow.
According to various embodiments, use of such apertures 206 as the
only path for providing gas to the gaps 204a, 204b, and desirably
using apertures 206 that lie in directions close to normal to the
heat sink surface 201b, 202b, ensures that air-bearing type
dynamics are optimized, and not compromised by gas flows from
larger apertures, or from sources other than through the heat sink
surface(s) 201b, 202b adjacent to the sheet 200, or by other
excessive lateral flow. In other embodiments gas may be provided to
the gaps 204a, 204b via other sources, such as in addition to the
apertures 206 or pores. Accordingly, aspects of the present
disclosure allow for power and energy savings by use of low gas
flows and solid-gas-solid conduction, such as relative to
conventional convective tempering processes.
FIGS. 22-25 show an exemplary embodiment of a cover glass
strengthening system 300 according to this disclosure. FIG. 22
shows a schematic cross-sectional diagram of the system 300, in
which a cover glass sheet can be cooled via conduction of heat from
the cover glass sheet, through a gas into a conductive heat sink.
The apparatus includes a hot zone 310, a cold zone 330, and a
transition gas bearing 320. Transition gas bearing 320 moves or
directs a cover glass article (e.g., cover glass sheet 400a) from
the hot zone 310 to the cold zone 330 such that no contact or
substantially no contact occurs between the cover glass and the
bearings. The hot zone 310 has gas bearings 312 each fed from a hot
zone plenum 318, and the bearings 312 have cartridge heaters 314
inserted into holes through the bearings 312, which serve to heat
the hot zone gas bearings 312 to a desired starting process
temperature. A cover glass sheet (hot zone) 400a is kept between
the hot zone gas bearings 312 for a duration long enough to bring
it to a desired pre-cooling temperature (e.g., above the transition
temperature).
In some embodiments, heating the sheet in the hot zone may be done
predominantly via conduction of heat from a heat sink through a
thin gas barrier. The conductive heating processes used in the hot
zone can be similar to, but the reverse of the cooling processes
described herein (e.g., pushing heat into the cover glass
sheet).
In some embodiments, gaps 316, between the hot zone gas bearings
312 and the cover glass sheet 400a, may be relatively large, on the
order of 0.05'' (1.27 mm) to 0.125'' (3.175 mm) or greater, since
the cover glass sheet 400a may be heated up relatively slowly and
thermal radiation from the hot gas bearings 312 into the cover
glass sheet 400a is adequate for this purpose. In other
embodiments, hot zone gap size may be as small as 150 microns per
side or 500 microns per side. Smaller gaps may be advantageous, in
some embodiments, because they enable the bearings to have better
"stiffness"--i.e., ability to centralize the cover glass and
therefore flatten it while it is in its softened state. In some
embodiments, the process may re-form the cover glass
sheets--flattening them--in the initial heating step, for example
via the pressure supplied by the gas bearings 312. In some
embodiments, the top and bottom hot zone bearings may be on
actuators, allowing for changing the gap width in a continuous
manner or, alternatively, allowing the cover glass to be brought
into the hot zone when the gap is large and then compressing the
gap to flatten the cover glass while it is still soft.
Process temperatures are dependent on a number of factors,
including cover glass composition, cover glass thickness, cover
glass properties (CTE, etc.), and desired level of strengthening.
Generally, the starting process temperature may be any value
between the cover glass transition temperature and the Littleton
softening point, or in some embodiments, even higher. For SLG, for
example, system 300 heats the cover glass sheet 400a to a
temperature between about (e.g., plus or minus 1%) 640 to about
730.degree. C. or between about 690 to about 730.degree. C. In some
embodiments, system 300 heats the glass sheet 400a to a temperature
from about (e.g., plus or minus 1%) 620 to about 800.degree. C.,
about 640 to about 770.degree. C., about 660 to about 750.degree.
C., about 680 to about 750.degree. C., about 690 to about
740.degree. C., or about 690 to about 730.degree. C.
The cover glass sheet 400a is heated to its desired starting
process temperature (e.g., above the cover glass transition
temperature), and it is then moved from the hot zone 310 to the
cold zone 330 using any suitable means. In some embodiments, moving
the cover glass sheet 400a from the hot zone 310 to the cold zone
330 may be accomplished by, for example (1) tilting the entire
assembly such that gravity acting on the cover glass sheet forces
it to move to the cold zone, (2) blocking off the gas flow from the
leftmost exit of the hot zone 310 (the sides are enclosed in this
embodiment), thereby forcing all of the gas emanating from all of
the gas bearings to exit from the rightmost exit of the cold zone,
causing fluid forces to be exerted on the cover glass sheet 400a
and causing it to move to the cold zone 330, or (3) by a
combination of (1) and (2))
The transition gas bearings 320 may be supplied with gas by
transition bearing plenums 328. The solid material thickness behind
the surfaces of the transition gas bearings 320 may be thin, of low
thermal mass and/or low thermal conductivity, allowing for reduced
heat conduction from the hot zone 310 to the cold zone 330. The
transition gas bearings 320 may serve as a thermal break or
transition between the two zones 310 and 330 and may serve to
transition from the larger gaps 316 of the hot zone down to small
gaps 336 of the cold zone 330. Further, the low thermal mass and/or
low thermal conductivity of transition gas bearings 320 limit(s)
the amount of heat transfer and therefore cooling experienced by
cover glass sheet 400a while passing past transition gas bearings
320.
Once the cover glass sheet (cold zone) 400b moves into the cold
zone 330 and into the channel 330a, it is stopped from exiting the
right side exit by a mechanical stop or any other suitable blocking
mechanism, shown as stop gate 341. Once the consumer electronic
glass or cover glass sheet 400b cools sufficiently that the center
has passed the glass transition (in the case, for example, of 1 mm
thick SLG, to below about 490.degree. C., corresponding in this
example to about 325.degree. C. at the surface), the stop gate 341
may be moved, unblocking cold zone channel 330a, and then the cover
glass sheet 400b may be removed from the system 300. If desired,
the cover glass sheet 400b may be left in the cold zone 330 until
somewhere near room temperature before removal.
As noted above, within hot zone 310, cover glass sheet 400 is
heated to a temperature above the cover glass transition
temperature of the cover glass sheet. In the embodiment shown in
FIG. 22, the cold zone 330 includes a channel 330a for receiving
heated cover glass sheet 400b through an opening 330b, conveying
the cover glass sheet 400b, and cooling the cover glass sheet 400b
in the cold zone. In one or more embodiments, the channel 330a
includes a conveyance system that may include gas bearings, roller
wheels, conveyor belt, or other means to physically transport the
cover glass sheet through the cold zone. As shown in FIG. 22, cold
zone 330 includes gas bearings 332 which are fed plenums 338 that
are separate from hot zone plenums 318 and transition plenums
328.
As shown in FIG. 22, the cold zone 330 includes one or more heat
sinks 331 disposed adjacent to the channel 330a. Where two heat
sinks are utilized, such heat sinks may be disposed on opposite
sides of the channel 330a, facing each other across a channel gap
330a. In some embodiments, the heat sinks include a plurality of
apertures 331a which form part of the gas bearing 332, and the
surfaces of the cold gas bearings 332 of the cold zone 330 serve as
the two heat sink surfaces. Due to the low air flow rate within
channel 330a and the small size of channel gap 330a, cover glass
sheet 400b is cooled within cold zone 330 primarily by conduction
of heat from the cover glass sheet across the gap and into the
solid heat sinks 331, without the cover glass sheet 400b touching
the heat sink surfaces.
In some embodiments, the heat sinks and/or the surfaces thereof may
be segmented. As noted above, in some embodiments, the heat sinks
may be porous, and in such embodiments, the apertures through which
the gas for gas bearings 332 is delivered are the pores of the
porous heat sinks. The plurality of apertures 332b, a gas source
and the channel gap 330a may be in fluid communication. In some
embodiments, the gas flows through the apertures 331a to form gas
cushions, layers or bearings in the channel gap 330a. The gas
cushions of some embodiments prevent the cover glass sheet 400b
from contacting the heat sink 331 surfaces. The gas also serves as
the gas through which the cover glass sheet 400b is cooled by
conduction more than by convection.
Because cooling occurs essentially by solid-to-solid heat
conduction across the gaps, issues not present in
convection-dominated cooling may need to be addressed. For example,
for tempering of a large, thin sheet, the sheet may be (1)
introduced quickly into the cold zone, optionally at higher speeds
than those typically used in convection-based quenching and/or (2)
the process is operated in a quasi-continuous mode, in which
multiple sheets are heated and cooled one after the other in a
continuous stream with little space between them, and where the
heat sink is actively cooled such that it reaches a thermal
equilibrium so that the front and trailing edges of the large
sheets have similar thermal history.
In some embodiments, the gas flowed through the apertures 331a
cools the heat sinks. In some embodiments, the gas flowed through
the apertures both facilitates heat conduction, from the cover
glass, across the gap, into the heat sinks, and also cools the heat
sinks 331. In some instances, a separate gas or fluid may be used
to cool the heat sinks 331. For instance, the heat sinks 331 may
include passages 334, for flowing a cooling fluid therethrough to
cool the heat sinks 331, as is more fully described with respect to
FIG. 23. The passages 334 can be enclosed.
Where two heat sinks are used (i.e., a first heat sink and the
second heat sink), one or more gas sources may be used to provide a
gas to the channel gap 330a. The gas sources may include the same
gas as one another or different gases. The channel gap 330a may,
therefore, include one gas, a mixture of gases from different gas
sources, or the same gas source. Exemplary gases include air,
nitrogen, carbon dioxide, helium or other noble gases, hydrogen and
various combinations thereof. The gas may be described by its
thermal conductivity when it enters the channel 330a just before it
begins to conductively cool the cover glass sheet 400b. In some
instances, the gas may have a thermal conductivity of about (e.g.,
plus or minus 1%) 0.02 W/(mK) or greater, about 0.025 W/(mK) or
greater, about 0.03 W/(mK) or greater, about 0.035 W/(mK) or
greater, about 0.04 W/(mK) or greater, about 0.045 W/(mK) or
greater, about 0.05 W/(mK) or greater, about 0.06 W/(mK) or
greater, about 0.07 W/(mK) or greater, about 0.08 W/(mK) or
greater, about 0.09 W/(mK) or greater, about 0.1 W/(mK) or greater,
about 0.15 W/(mK) or greater, or about 0.2 W/(mK) or greater).
The processes and systems described herein allow for high heat
transfer rates which, as discussed above, allow for a strengthening
degree of temperature differential to form within even a very thin
cover glass sheet. Using air as the gas, with gaps between the
cover glass sheet and the heat sinks, heat transfer rates as high
as 350, 450, 550, 650, 750, 1000, and 1200 kW/m.sup.2 or more are
possible through conduction alone. Using helium or hydrogen, heat
transfer rates of 5000 kW/m.sup.2 or more can be achieved.
The heat sinks 331 of one or more embodiments may be stationary or
may be movable to modify the thickness of the channel gap 330a. The
thickness of the cover glass sheet 400b may be in a range from
about 0.4 times the thickness to about 0.6 times the thickness of
channel gap 300a, which is defined as the distance between the
opposing surfaces of the heat sinks 331 (e.g., upper and lower
surface of heat sinks 331 in the arrangement of FIG. 22). In some
instances, the channel gap is configured to have a thickness
sufficient such that the heated cover glass sheet is cooled by
conduction more than by convection.
In some embodiments, the channel gap may have a thickness such that
when cover glass sheet 400b is being conveyed through or located
within the channel 330a, the distance between the major surfaces of
the cover glass sheet 400b and the heat sink surface (e.g., the gap
size discussed above) is about (e.g., plus or minus 1%) 100 .mu.m
or greater (e.g., in the range from about 100 .mu.m to about 200
.mu.m, from about 100 .mu.m to about 190 .mu.m, from about 100
.mu.m to about 180 .mu.m, from about 100 .mu.m to about 170 .mu.m,
from about 100 .mu.m to about 160 .mu.m, from about 100 .mu.m to
about 150 .mu.m, from about 110 .mu.m to about 200 .mu.m, from
about 120 .mu.m to about 200 .mu.m, from about 130 .mu.m to about
200 .mu.m, or from about 140 .mu.m to about 200 .mu.m). In some
embodiments, the channel gap may have a thickness such that when
cover glass sheet 400b is being conveyed through the channel, the
distance between the cover glass sheet and the heat sink surface
(the gap or gaps 336) is about (e.g., plus or minus 1%) 100 .mu.m
or less (e.g., in the range from about 10 .mu.m to about 100 .mu.m,
from about 20 .mu.m to about 100 .mu.m, from about 30 .mu.m to
about 100 .mu.m, from about 40 .mu.m to about 100 .mu.m, from about
10 .mu.m to about 90 .mu.m, from about 10 .mu.m to about 80 .mu.m,
from about 10 .mu.m to about 70 .mu.m, from about 10 .mu.m to about
60 .mu.m, or from about 10 .mu.m to about 50 .mu.m). The total
thickness of the channel gap 330a is dependent on the thickness of
the cover glass sheet 400b, but can be generally characterized as 2
times the distance between the heat sink surface and the cover
glass sheet, plus the thickness of the cover glass sheet. In some
embodiments, the distance or gaps 336 between the cover glass sheet
and the heat sinks may not be equal. In such embodiments, the total
thickness of the channel gap 330a may be characterized as the sum
of the distances between the cover glass sheet and each heat sink
surface, plus the thickness of the cover glass sheet.
In some instances, the total thickness of the channel gap may be
less than about (e.g., plus or minus 1%) 2500 .mu.m (e.g., in the
range from about 120 .mu.m to about 2500 .mu.m, about 150 .mu.m to
about 2500 .mu.m, about 200 .mu.m to about 2500 .mu.m, about 300
.mu.m to about 2500 .mu.m, about 400 .mu.m to about 2500 .mu.m,
about 500 .mu.m to about 2500 .mu.m, about 600 .mu.m to about 2500
.mu.m, about 700 .mu.m to about 2500 .mu.m, about 800 .mu.m to
about 2500 .mu.m, about 900 .mu.m to about 2500 .mu.m, about 1000
.mu.m to about 2500 .mu.m, about 120 .mu.m to about 2250 .mu.m,
about 120 .mu.m to about 2000 .mu.m, about 120 .mu.m to about 1800
.mu.m, about 120 .mu.m to about 1600 .mu.m, about 120 .mu.m to
about 1500 .mu.m, about 120 .mu.m to about 1400 .mu.m, about 120
.mu.m to about 1300 .mu.m, about 120 .mu.m to about 1200 .mu.m, or
about 120 .mu.m to about 1000 .mu.m). In some instances, the total
thickness of the channel gap may be about 2500 .mu.m or more (e.g.,
in the range from about 2500 .mu.m to about 10,000 .mu.m, about
2500 .mu.m to about 9,000 .mu.m, about 2500 .mu.m to about 8,000
.mu.m, about 2500 .mu.m to about 7,000 .mu.m, about 2500 .mu.m to
about 6,000 .mu.m, about 2500 .mu.m to about 5,000 .mu.m, about
2500 .mu.m to about 4,000 .mu.m, about 2750 .mu.m to about 10,000
.mu.m, about 3000 .mu.m to about 10,000 .mu.m, about 3500 .mu.m to
about 10,000 .mu.m, about 4000 .mu.m to about 10,000 .mu.m, about
4500 .mu.m to about 10,000 .mu.m, or about 5000 .mu.m to about
10,000 .mu.m).
The apertures 331a in the heat sink 331 may be positioned to be
perpendicular to the heat sink surface or may be positioned at an
angle of 20 degrees or less, such as about (e.g., plus or minus 1%)
15 degrees or less, about 10 degrees or less or about 5 degrees or
less) from perpendicular to the heat sink surface.
In some embodiments, the material behind the heat sink (cold
bearing 332) surfaces can be any suitable material having high heat
transfer rates, including metals (e.g., stainless steel, copper,
aluminum), ceramics, carbon, etc. This material may be relatively
thick compared to the material behind the surfaces of the
transition bearings 320, as shown in FIG. 22, such that heat sink
can easily accept relatively large amounts of thermal energy. In an
exemplary embodiment, the material of the heat sinks 331 is
stainless steel.
FIG. 23 is a cut-away perspective cross-section of an apparatus
similar to that of FIG. 22, albeit reversed from right to left, and
comprising additionally a load/unload zone 340, next to cold zone
330 of system 300, including a load/unload gas bearing 342 with a
cover glass sheet 400c positioned thereon. Also, the apparatus of
FIG. 23 uses tight channel gaps (not indicated on the figure) in
hot zone 310, transition bearing 320, and cold zone 330.
The inset in FIG. 23 shows an alternative embodiment of a cold zone
gas bearing 332a, in which the gas bearing 322a is actively cooled
by coolant channels 334, between gas bearing feed holes 333, where
the feed holes feed the apertures in the surface of the bearing
322a. The cooling channels 334 are defined between heat sink
segments 333b, which are assembled together to form the heat sink
331 and the surface thereof facing the cover glass sheet 400b.
The cooling channels 334 may be positioned very near the surface of
the heat sink 331, in the solid material of the gas bearing 332,
with a region of solid bearing material between the heat sink/gas
bearing surface and the nearest-the-surface edge of the coolant
channel 334, having the same width as the nearest-the-surface edge
of the coolant channel 334. Accordingly, in some embodiments there
is no region of reduced cross section in the solid material of the
heat sink 331/gas bearing 332a between a coolant channel 334 and
the surface facing the cover glass 400b. This differs from the
typical convective gas cooling equipment, because the high gas flow
rates mandate that significant space be provided in the middle of
the array of gas nozzles for the gas flows to escape. Where active
cooling is used, heat sink 331/gas bearing 332a has a region of
reduced cross section in the solid material of the gas nozzle
design, relative to the solid material nearest the cover glass
surface. The reduced cross section region is generally positioned
between the active cooling fluid and cover glass sheet under
treatment, in order to give a high-volume path for the large volume
of heated gas returning from the sheet.
FIG. 24 shows yet another alternative embodiment of a cold zone gas
bearing 332, like that of the inset of FIG. 23. In this embodiment,
coolant channels 334 are formed between a gas bearing feed member
335, containing gas bearing feed holes 333, and a gas bearing face
member 337a, which provides the cover glass sheet 400b facing
surface of the gas bearing 332. FIG. 25 shows yet another
alternative cold zone gas bearing 332c having a similar structure
to the embodiment of FIG. 24, but having a porous member 339
between a bearing plate member 337b and cover glass sheet 400b,
such that porous member 339 forms the surface facing the cover
glass sheet 400b.
It should be understood that in various embodiments, the cover
glass strengthening processes and systems described herein in
relation to FIGS. 16-26 may be used or operated to form a cover
glass or glass ceramic article (such as cover glass sheet 500)
having any combination of features, characteristics, dimensions,
physical properties, etc. of any of the cover glass article
embodiments discussed herein.
Cover glass sheets having undergone the thermal strengthening
processes described herein may be further processed by undergoing
ion exchange to further enhance their strength. Ion-exchanging the
surface of cover glasses heat strengthened as described herein may
increase the above-described compressive stresses by at least 20
MPa, such as at least 50 MPa, such as at least 70 MPa, such as at
least 80 MPa, such as at least 100 MPa, such as at least 150 MPa,
such as at least 200 MPa, such as at least 300 MPa, such as at
least 400 MPa, such as at least 500 MPa, such as at least 600 MPa
and/or no more than 1 GPa, in some such contemplated
embodiments.
Systems and Processes for Thermal Conditioning and/or Heating Cover
Glass Sheet
In addition to thermally strengthening thin cover glass sheets, the
processes and systems described herein can be used for additional
thermal conditioning processes as well. While cooling is
specifically discussed herein, the systems and processes can be
used to transfer heat into the cover glass sheet via a conductive
method. Accordingly, additional embodiments of the processes of the
current disclosure, including heating through a gas by conduction
more than convection. Such a process or method 700 is illustrated
in the flow chart of FIG. 26.
The method 700 includes two main steps. The first step, step 710,
involves providing an article, such as a cover glass sheet, having
at least one surface. The second step, step 720, involves heating
or cooling a portion of the surface of the article, up to and
including the entire surface of the article. Step 720 is performed
by conduction more than by convection through a gas from or to a
heat source or a heat sink source as shown in sub-part 720a, and is
performed sufficiently to complete thermal conditioning of the
article or the portion of the surface of the article in sub-part
720b, and the conduction of the cooling/heating of step 720 is
performed at a high rate of heat transfer, at least 450 kW/m.sup.2
of the area of the portion in sub-part 720b.
For example, an article can be thermally conditioned--i.e., either
heated or cooled--by cooling or heating a portion of the surface of
the article, up to and including the entire surface of the article
(the portion having an area), by conduction more than by
convection, the conduction mediated through a gas to or from a heat
sink or a heat source and not through solid-to-solid contact,
sufficiently to complete a thermal conditioning of the article or
of the portion of the surface of the article, and the conduction
being performed, during at least some time of the heating or
cooling, at a rate of at least 450, 550, 650, 750, 800, 900, 1000,
1100, 1200, 1500, 2000, 3000, 4000 or even 5000 or more kW per
square meter.
In addition to tempering, the high rates of thermal power transfer
provided by the systems and methods discussed herein allow for
thermal processing or conditioning of all kinds, including heating
and cooling during tempering, edge strengthening of cover glass,
firing or sintering of ceramics, glasses, or other materials, and
so forth. Additionally, since the heat is extracted or delivered
primarily by conduction, tight control is provided over the thermal
history and the heat distribution in the treated article while
preserving surface smoothness and quality. Accordingly, in yet
another aspect of the present disclosure, tight control is provided
over the thermal history and the heat distribution in the treated
article, since the heat is extracted or delivered primarily by
conduction, yet surface smoothness and quality are preserved.
Accordingly, it will be possible to use the systems and methods of
the present disclosure to intentionally vary the stress profile
from the strengthening process, both in the thickness direction and
in the directions in which the plane of the sheet lies, by varying
gaps, varying heat sink/source materials, varying heat sink/source
temperatures, varying the gas mixture--and all these may be varied
by position along the path of the sheet as it moves, or across the
path of the sheet, or potentially in time also, not merely with
position (for most of the variables).
Devices, Products and Structures Incorporating Strengthened Cover
Glass Sheets
The strengthened cover glass or glass-ceramic articles and sheets
discussed herein have a wide range of uses in a wide range of
articles, devices, products, structures, etc. Discussion of cover
glass or glass-ceramics herein is also referred to as consumer
electronic glass. The cover glass or glass-ceramic of according to
the present disclosure may be used on any surface of electronic
devices, mobile phones, portable media players, televisions,
notebook computers, watches, user wearable devices (e.g., Fitbit),
cameras lenses, camera displays, household appliances, tablet
computer displays, and any other electronic devices which may
require a surface according to the properties and dimensions
described herein.
Referring to FIG. 27, a structure 1010, such as a building, house,
vehicle, etc., includes a glass or glass-ceramic article 1012 in
the form of a window, portion of walls (e.g., surfaces), dividers,
etc. In contemplated embodiments, the glass or ceramic article 1012
may be strengthened such that the glass or ceramic article 1012 has
a negative tensile stress on or near surfaces thereof, balanced by
a positive tensile stress internal thereto, as disclosed herein.
Further, the glass or glass-ceramic article 1012 may have a
composition that resists chemicals and/or corrosion as may be
present in outdoor environments by having a relatively high silicon
dioxide content, such as at least 70% silicon dioxide by weight,
such as at least 75% by weight.
According to an exemplary embodiment, the glass or glass-ceramic
article 1012 has major surfaces orthogonal to a thickness thereof
(see generally sheet 500 as shown in FIG. 4), where the major
surfaces have a large area (e.g., at least 5 cm.sup.2, at least 9
cm.sup.2, at least 15 cm.sup.2, at least 50 cm.sup.2, at least 250
cm.sup.2) relative to glass or glass-ceramic articles used in other
applications (e.g., lenses, battery components, etc.). In
contemplated embodiments, total light transmission through the
glass or glass-ceramic articles 1012 is at least about 50% (e.g.,
at least 65%, at least 75%) from wavelengths of about 300 nm to
about 800 nm, when the glass or glass ceramic article 1012 has
thicknesses as disclosed herein, such as a thickness of less than 5
cm, less than 3 cm, less than 2 cm, less than 1.75 cm, less than
1.5 cm, less than 1 cm, less than 5 mm, less than 3 mm, less than 2
mm, less than 1.75 mm, less than 1.5 mm, less than 1 mm, less than
0.8 mm, less than 0.6 mm, less than 0.5 mm, less than 0.4 mm, less
than 0.2 mm, and/or at least 10 micrometers, such as at least 50
micrometers.
Thin thicknesses of the glass or glass-ceramic article 1012 may not
harm the function of the glass or glass-ceramic article 1012 in
architectural, automotive, or other applications relative to
conventional articles because the high level of strength of the
glass or glass-ceramic article 1012 provided by the inventive
processes disclosed herein. Thin glass or glass-ceramic articles
1012 may be particularly useful in such architectural, automotive,
consumer electronics, or other applications because the glass or
glass ceramic article 1012 may be lighter than conventional such
articles, reducing the weight of the corresponding overall
structure. For automobiles, a result may be greater fuel
efficiency. For buildings, a result may be sturdier or less
resource-intensive structures. For consumer electronics, a lighter
device with greater impact resistance and/or resilience to
recurring drops or impacts. In other contemplated embodiments,
glass or glass-ceramic articles disclosed herein may have areas of
lesser magnitude, greater thicknesses, transmit less light, and/or
may be used in different applications, such as those disclosed with
regard to FIGS. 27-30, for example.
Referring to FIG. 28, a surface 1110 includes a glass or glass
ceramic article 1112, manufactured as disclosed herein and/or with
any combination of stress profiles, structures and/or physical
properties discussed herein, that functions as a countertop and/or
as a portion of a display. In some embodiments, total transmission
through the cover glass or glass ceramic articles 1012 is at least
about 30% (e.g., at least 50%) from infrared wavelengths of about
800 nm to about 1500 nm, facilitating use of the surface 1110 as a
cooktop. In some embodiments, the cover glass or glass-ceramic
article 1112 has a coefficient of thermal expansion (CTE) from
about 10.times.10.sup.-7.degree. C..sup.-1 to about
140.times.10.sup.-7.degree. C..sup.-1, about
20.times.10.sup.-7.degree. C..sup.-1 to about
120.times.10.sup.-7.degree. C..sup.-1, about
30.times.10.sup.-7.degree. C..sup.-1 to about
100.times.10.sup.-7.degree. C..sup.-1, about
40.times.10.sup.-7.degree. C..sup.-1 to about
100.times.10.sup.-7.degree. C..sup.-1, about
50.times.10.sup.-7.degree. C..sup.-1 to about
100.times.10.sup.-7.degree. C..sup.-1, or about
60.times.10.sup.-7.degree. C..sup.-1 to about
120.times.10.sup.-7.degree. C..sup.-1. In various embodiments, the
processes are ideally suited for glass compositions having moderate
to high CTEs. Example cover glasses that work well with the
processes described herein include alkali aluminosilicates, such as
Corning's.RTM. Gorilla.RTM. Glasses, boroaluminosilicates, and
soda-lime glasses. In some embodiments, the cover glasses used have
CTEs greater than 40, greater than 50, greater than 60, greater
than 70, greater than 80, or greater than
90.times.10.sup.-7/.degree. C. Some such CTEs may be particularly
low for thermal tempering as disclosed herein, where the degree of
negative tensile stress is no more than 50 MPa and/or at least 10
MPa.
Referring to FIG. 29, a device 1210 (e.g., handheld computer,
tablet, portable computer, cellular phone, television, watch,
display board, etc.) includes one or more cover glass or
glass-ceramic articles 1212, 1214, 1216, manufactured as disclosed
herein and/or with any combination of stress profiles, structures
and/or physical properties as disclosed herein, and further
includes electronic components 1218 (e.g., a display, and
electrical display, a controller, a memory, a microchip, etc.) and
a housing 1220. In embodiments, electrical components 1218 and/or
the electrical display may include a liquid crystal display and/or
at least one light emitting diode (LED). In embodiments, the
electronic display may be a touch sensitive display. In further
embodiments, the glass-based layer forming or covering the
electronic display may include a surface feature on the first or
second major surface for haptic feedback for a user. For example,
raised projections, ridges, contours, or bumps are non-limiting
example surface features for haptic feedback. In embodiments,
electrical components 1218 are provided at least partially within
housing 1220. In embodiments, electrical components 1218 are
provided completely within housing 1220. In contemplated
embodiments, the housing 1220 may be or include a cover glass or
glass-ceramic article as disclosed herein. In contemplated
embodiments, a substrate 1222 for the electronic components 1218
may be a cover glass or glass-ceramic article as disclosed
herein.
In some embodiments, the cover glass or glass ceramic articles
1212, 1214 may function as frontplane and backplane substrates, and
the cover glass or glass ceramic article 1216 may function as a
cover glass in the device 1210. According to an exemplary
embodiment, the cover glass or glass-ceramic article 1216 of the
device 1210 is an alkali-aluminosilicate glass. Such composition
may allow the cover glass or glass-ceramic article 1216 to be
strengthened by thermal tempering, as disclosed herein, and may be
additionally strengthened by ion-exchange, providing a particularly
high degree of negative tensile stress (e.g., at least 200 MPa, at
least 250 MPa) at or near surfaces thereof. In other embodiments,
the cover glass or glass-ceramic article 1216 may include sodium
carbonate, calcium oxide, calcium magnesium carbonate, silicon
dioxide (e.g., at least 70% by weight), aluminum oxide, and/or
other constituents; and may be strengthened by the inventive
processes disclosed herein. The cover glass or glass ceramic
article 1216 may be particularly thin or otherwise structured, such
as having any of the dimensions, properties, and/or compositions as
disclosed herein.
In embodiments, housing 1220 may include a front surface, a back
surface, and at least one side surface 1220. Housing 1220 may
include one or more glass-based layers including cover glass or
glass-ceramic articles manufactured as disclosed herein and/or with
any combination of stress profiles, structures and/or physical
properties discussed herein. In embodiments, the glass-based layer
may be a cover glass or glass-ceramic article as disclosed herein.
The glass based layer (e.g., 1212, 1214, 1216) may form any surface
of a consumer electronic product. In one or more embodiments, the
glass-based layer extends across the housing front surface from at
least one side surface (e.g., 1220) to an opposite side surface. In
embodiments, the glass-based layer is provided at or adjacent the
front surface of housing 1220. In further embodiments, the
glass-based layer may include a surface feature on the first or
second major surface for haptic feedback for a user. For example,
raised projections, ridges, contours, or bumps are non-limiting
example surface features for haptic feedback. In embodiments, glass
based layer (e.g., 1212, 1214, 1216) may be shaped in 1-dimension,
2-dimensions, 2.5-dimensions (e.g., curvature at the edge of a
display glass), or 3-dimensions.
In other embodiments, the glass-based layer (e.g., 1212, 1214,
1216) may have at least one beveled or curved edge, including an
embodiment where the entire outside perimeter of the glass-based
layer is beveled or curved. In embodiments, the average thickness
of the glass-based layer may not exceed 1.5 mm, may not exceed 1.0
mm, may not exceed 0.7 mm, may not exceed 0.5 mm, or may have an
average thickness within a range from about 0.5 mm to about 1.0 mm,
or about 0.1 mm to about 1.5 mm, or an average thickness from about
0.5 mm to about 0.7 mm. In yet other embodiments, the one or more
of the major surfaces of the glass-based layer may include an
anti-scratch layer, an antireflection layer, and an antiglare
layer. The one or more major surfaces of the glass-based layer may
also include any combination or all of these layers.
The cover glass or glass-ceramic article may include a glass
material that is substantially optically clear, transparent and
free from light scattering. In such embodiments, the cover glass
material may exhibit an average light transmission over a
wavelength range from about 400 nm to about 780 nm of about 85% or
greater, about 86% or greater, about 87% or greater, about 88% or
greater, about 89% or greater, about 90% or greater, about 91% or
greater or about 92% or greater. In one or more alternative
embodiments, the glass material may be opaque or exhibit an average
light transmission over a wavelength range from about 400 nm to
about 780 nm of less than about 10%, less than about 9%, less than
about 8%, less than about 7%, less than about 6%, less than about
5%, less than about 4%, less than about 3%, less than about 2%,
less than about 1%, or less than about 0%. In some embodiments,
these light reflectance and transmittance values may be a total
reflectance or total transmittance (taking into account reflectance
or transmittance on both major surfaces of the glass material). The
glass material may optionally exhibit a color, such as white,
black, red, blue, green, yellow, orange, etc.
Referring now to FIG. 30, a cover glass or glass-ceramic article
1310, manufactured according to processes disclosed herein and/or
with any combination of stress profiles, structures and/or physical
properties as disclosed herein, has curvature and/or a variable
cross-sectional dimension D. Such articles may have thicknesses
disclosed herein as an average of dimension D or as a maximum value
of dimension D. While the cover glass or glass-ceramic article 1310
is shown as a curved sheet, other shapes, such as more complex
shapes, may be strengthened by processes disclosed herein. In
contemplated embodiments, the cover glass or glass ceramic article
1310 may be used as a front pane, back pane, or on any surface of a
consumer electronic product.
In various embodiments, cover glass material manufactured according
to processes disclosed herein, and/or with any combination of
stress profiles, structures and/or physical properties as disclosed
herein, is useful to form at least one sheet of a cover
glass-interlayer-cover glass laminate, such as used in automotive
glass sidelights. Stronger and thinner laminates can be produced,
resulting in weight and cost savings and fuel efficiency increases.
Desirably, a thermally strengthened thin sheet may be cold bent
(see generally FIG. 30) and laminated to a formed thicker glass,
providing an easy and reliable manufacturing process not requiring
any hot forming/shaping of the thin sheet.
Glass and Glass Ceramic Materials for Thermally Strengthened Cover
Glass Sheets
The systems and methods discussed may be used to thermally
condition, strengthen and/or temper a wide variety of cover glass
and/or ceramic materials.
The processes and systems described herein may generally be used
with almost any glass composition, and some embodiments can be used
with glass laminates, glass ceramics, and/or ceramics. In various
embodiments, the processes can be used with glass compositions
having high CTEs. In embodiments, cover glasses strengthened via
the processes and systems discussed herein include alkali
aluminosilicates, such as Corning's.RTM. Gorilla.RTM. Glasses, SLG,
soda- or alkali-free glasses and the like. In some embodiments,
cover glasses strengthened via the processes and systems discussed
herein have CTEs of greater than 40.times.10.sup.-7/.degree. C.,
greater than 50.times.10.sup.-7/.degree. C., greater than
60.times.10.sup.-7/.degree. C., greater than
70.times.10.sup.-7/.degree. C., greater than
80.times.10.sup.-7/.degree. C., or greater than
90.times.10.sup.-7/.degree. C.
In some applications and embodiments, cover glasses strengthened
via the processes and systems discussed herein (such as cover glass
sheet 500) may have a composition configured for chemical
durability. In some such embodiments, the composition comprises at
least 70% silicon dioxide by weight, and/or at least 10% sodium
oxide by weight, and/or at least 7% calcium oxide by weight.
Conventional articles of such compositions may be difficult to
chemically temper to a deep depth, and/or may be difficult, if not
impossible, to thermally temper by conventional processes to a
sufficient magnitude of negative surface tensile stress for thin
thicknesses, such as due to fragility and forces of conventional
processes. However, in contemplated embodiments, inventive
processes disclosed herein allow a strengthened cover glass or
glass-ceramic article or sheet, such as cover glass sheet 500, with
such a composition, where negative tensile stress extends into the
respective strengthened cover glass or glass-ceramic sheet to a
distance of at least 10% of the thickness of the strengthened cover
glass or glass-ceramic sheet from at least one of the first and
second surfaces (e.g., surfaces 510, 520 of cover glass sheet 500),
such as at least 12% of the thickness, 15% of the thickness, 16% of
the thickness, 17% of the thickness, 18% of the thickness, 19% of
the thickness, 20% of the thickness, or 21% of the thickness.
In some embodiments, the cover glass or glass-ceramic sheets and
articles strengthened as discussed herein have one or more coatings
that are placed on the cover glass prior to the thermal
strengthening of the cover glass sheet. The processes discussed
herein can be used to produce strengthened cover glass sheets
having one or more coatings, and, in some such embodiments, the
coating is placed on the cover glass prior to thermal strengthening
and is unaffected by the thermal strengthening process. Specific
coatings that are advantageously preserved on cover glass sheets of
the present disclosure include low E coatings, reflective coatings,
antireflective coatings, anti-fingerprint coatings, cut-off
filters, pyrolytic coatings, etc.
According to an exemplary embodiment, cover glass or glass-ceramic
sheets or articles discussed herein, for example articles 1212,
1214 of the device 1210 shown in FIG. 29, are boro-aluminosilicate
glasses. In some embodiments cover glass or glass ceramic sheets or
articles discussed herein, for example articles 1212, 1214 of the
device 1210 shown in FIG. 29, are generally non-alkali glasses, yet
still have stress profiles and structures as disclosed herein. Such
composition may reduce the degree of relaxation of the glass,
facilitating coupling of transistors thereto. In some embodiments,
the cover glass sheets/articles discussed herein are flexible glass
sheets. In other embodiments, the cover glass sheets/articles
discussed herein comprise a laminate of two or more cover glass
sheets.
In some contemplated embodiments, cover glasses strengthened via
the processes and systems discussed herein (such as cover glass
sheet 500) may include an amorphous substrate, a crystalline
substrate or a combination thereof, such as a glass-ceramic
substrate. Cover glasses strengthened via the processes and systems
discussed herein (such as cover glass sheet 500) may include an
alkali aluminosilicate glass, alkali containing borosilicate glass,
alkali aluminophosphosilicate glass or alkali aluminoborosilicate
glass. In one or more embodiments, cover glasses strengthened via
the processes and systems discussed herein (such as cover glass
sheet 500), in portions thereof not ion-exchanged, may include a
cover glass having a composition, in mole percent (mol %),
including: SiO.sub.2 in the range from about (e.g., plus or minus
1%) 40 to about 80 mol %, Al.sub.2O.sub.3 in the range from about
10 to about 30 mol %, B.sub.2O.sub.3 in the range from about 0 to
about 10 mol %, R.sub.2O in the range from about 0 to about 20 mol
%, and/or RO in the range from about 0 to about 15 mol %. In some
contemplated embodiments, the composition may include either one or
both of ZrO.sub.2 in the range from about 0 to about 5 mol % and
P.sub.2O.sub.5 in the range from about 0 to about 15 mol %. In some
contemplated embodiments, TiO.sub.2 can be present from about 0 to
about 2 mol %.
In some contemplated embodiments, compositions used for the
strengthened cover glass or glass-ceramic sheet or article
discussed herein may be batched with 0-2 mol % of at least one
fining agent selected from a group that includes Na.sub.2SO.sub.4,
NaCl, NaF, NaBr, K.sub.2SO.sub.4, KCl, KF, KBr, and SnO.sub.2. The
cover glass composition according to one or more embodiments may
further include SnO.sub.2 in the range from about 0 to about 2 mol
%, from about 0 to about 1 mol %, from about 0.1 to about 2 mol %,
from about 0.1 to about 1 mol %, or from about 1 to about 2 mol %.
Cover glass compositions disclosed herein for the strengthened
cover glass or glass-ceramic sheet 500 may be substantially free of
As.sub.2O.sub.3 and/or Sb.sub.2O.sub.3, in some embodiments.
In contemplated embodiments, the strengthened cover glass or
glass-ceramic sheet or article discussed herein may include alkali
aluminosilicate cover glass compositions or alkali
aluminoborosilicate glass compositions that are further
strengthened via an ion exchange process. One example cover glass
composition comprises SiO.sub.2, B.sub.2O.sub.3 and Na.sub.2O,
where (SiO.sub.2+B.sub.2O.sub.3).gtoreq.66 mol. %, and/or
Na.sub.2O.gtoreq.9 mol. %. In an embodiment, the cover glass
composition includes at least 6 wt. % aluminum oxide. In a further
embodiment, the strengthened cover glass or glass-ceramic sheet or
article discussed herein may include a glass composition with one
or more alkaline earth oxides, such that a content of alkaline
earth oxides is at least 5 wt. %. Suitable cover glass
compositions, in some embodiments, further comprise at least one of
K.sub.2O, MgO and CaO. In a particular embodiment, the cover glass
compositions used in the strengthened cover glass or glass-ceramic
sheet or article discussed herein can comprise 61-75 mol. %
SiO.sub.2; 7-15 mol. % Al.sub.2O.sub.3; 0-12 mol. % B.sub.2O.sub.3;
9-21 mol. % Na.sub.2O; 0-4 mol. % K.sub.2O; 0-7 mol. % MgO; and/or
0-3 mol. % CaO.
A further example cover glass composition suitable for the
strengthened cover glass or glass-ceramic sheet or article
discussed herein comprises: 60-70 mol. % SiO.sub.2; 6-14 mol. %
Al.sub.2O.sub.3; 0-15 mol. % B.sub.2O.sub.3; 0-15 mol. % Li.sub.2O;
0-20 mol. % Na.sub.2O; 0-10 mol. % K.sub.2O; 0-8 mol. % MgO; 0-10
mol. % CaO; 0-5 mol. % ZrO.sub.2; 0-1 mol. % SnO.sub.2; 0-1 mol. %
CeO.sub.2; less than 50 ppm As.sub.2O.sub.3; and less than 50 ppm
Sb.sub.2O.sub.3; where 12 mol.
%.ltoreq.(Li.sub.2O+Na.sub.2O+K.sub.2O).ltoreq.20 mol. % and/or 0
mol. %.ltoreq.(MgO+CaO).ltoreq.10 mol. %. A still further example
glass composition suitable for the strengthened cover glass or
glass-ceramic sheet or article discussed herein comprises:
63.5-66.5 mol. % SiO.sub.2; 8-12 mol. % Al.sub.2O.sub.3; 0-3 mol. %
B.sub.2O.sub.3; 0-5 mol. % Li.sub.2O; 8-18 mol. % Na.sub.2O; 0-5
mol. % K.sub.2O; 1-7 mol. % MgO; 0-2.5 mol. % CaO; 0-3 mol. %
ZrO.sub.2; 0.05-0.25 mol. % SnO.sub.2; 0.05-0.5 mol. % CeO.sub.2;
less than 50 ppm As.sub.2O.sub.3; and less than 50 ppm
Sb.sub.2O.sub.3; where 14 mol.
%.ltoreq.(Li.sub.2O+Na.sub.2O+K.sub.2O).ltoreq.18 mol. % and/or 2
mol. %.ltoreq.(MgO+CaO).ltoreq.7 mol. %.
In particular contemplated embodiments, an alkali aluminosilicate
glass composition suitable for the strengthened cover glass or
glass-ceramic sheet or article discussed herein comprises alumina,
at least one alkali metal and, in some embodiments, greater than 50
mol. % SiO.sub.2, in other embodiments at least 58 mol. %
SiO.sub.2, and in still other embodiments at least 60 mol. %
SiO.sub.2, wherein the ratio
(Al.sub.2O.sub.3+B.sub.2O.sub.3)/Emodifiers (i.e., sum of
modifiers) is greater than 1, where in the ratio the components are
expressed in mol. % and the modifiers are alkali metal oxides. This
cover glass composition, in particular embodiments, comprises:
58-72 mol. % SiO.sub.2; 9-17 mol. % Al.sub.2O.sub.3; 2-12 mol. %
B.sub.2O.sub.3; 8-16 mol. % Na.sub.2O; and/or 0-4 mol. % K.sub.2O,
wherein the ratio (Al.sub.2O.sub.3+B.sub.2O.sub.3)/Emodifiers
(i.e., sum of modifiers) is greater than 1. In still another
embodiment, the strengthened cover glass or glass-ceramic sheet 500
may include an alkali aluminosilicate glass composition comprising:
64-68 mol. % SiO.sub.2; 12-16 mol. % Na.sub.2O; 8-12 mol. %
Al.sub.2O.sub.3; 0-3 mol. % B.sub.2O.sub.3; 2-5 mol. % K.sub.2O;
4-6 mol. % MgO; and 0-5 mol. % CaO, wherein: 66 mol.
%.ltoreq.SiO.sub.2+B.sub.2O.sub.3+CaO.ltoreq.69 mol. %;
Na.sub.2O+K.sub.2O+B.sub.2O.sub.3+MgO+CaO+SrO>10 mol. %; 5 mol.
%.ltoreq.MgO+CaO+SrO.ltoreq.8 mol. %;
(Na.sub.2O+B.sub.2O.sub.3)--Al.sub.2O.sub.3.ltoreq.2 mol. %; 2 mol.
%.ltoreq.Na.sub.2O--Al.sub.2O.sub.3.ltoreq.6 mol. %; and 4 mol.
%.ltoreq.(Na.sub.2O+K.sub.2O)--Al.sub.2O.sub.3.ltoreq.10 mol. %. In
an alternative embodiment, the strengthened cover glass or
glass-ceramic sheet or articles discussed herein may comprise an
alkali aluminosilicate glass composition comprising: 2 mol. % or
more of Al.sub.2O.sub.3 and/or ZrO.sub.2, or 4 mol. % or more of
Al.sub.2O.sub.3 and/or ZrO.sub.2.
In contemplated embodiments, examples of suitable glass ceramics
for the strengthened cover glass or glass-ceramic sheet or articles
discussed herein may include Li.sub.2O--Al.sub.2O.sub.3--SiO.sub.2
system (i.e. LAS-System) glass ceramics,
MgO--Al.sub.2O.sub.3--SiO.sub.2 system (i.e. MAS-System) glass
ceramics, and/or glass ceramics that include a predominant crystal
phase including .beta.-quartz solid solution, .beta.-spodumene ss,
cordierite, and lithium disilicate. The strengthened cover glass or
glass-ceramic sheet or article discussed herein may be
characterized by the manner in which it is formed. For instance,
the strengthened cover glass or glass-ceramic sheet or article
discussed herein may be characterized as float-formable (i.e.,
formed by a float process), down-drawable and, in particular,
fusion-formable or slot-drawable (i.e., formed by a down draw
process such as a fusion draw process or a slot draw process).
A float-formable strengthened cover glass or glass-ceramic sheet or
article may be characterized by smooth surfaces and consistent
thickness, and is made by floating molten cover glass on a bed of
molten metal, typically tin. In an example process, molten cover
glass or glass-ceramic that is fed onto the surface of the molten
tin bed forms a floating glass or glass-ceramic ribbon. As the
cover glass ribbon flows along the tin bath, the temperature is
gradually decreased until the cover glass or glass-ceramic ribbon
solidifies into a solid cover glass or glass-ceramic article that
can be lifted from the tin onto rollers. Once off the bath, the
cover glass or glass-ceramic article can be cooled further and
annealed to reduce internal stress. Where the cover glass or
glass-ceramic article is a glass ceramic, the cover glass article
formed from the float process may be subjected to a ceramming
process by which one or more crystalline phases are generated.
Down-draw processes produce cover glass or glass-ceramic articles
having a consistent thickness that possess relatively pristine
surfaces. Because the average flexural strength of the cover glass
or glass-ceramic article is controlled by the amount and size of
surface flaws, a pristine surface that has had minimal contact has
a higher initial strength. When this high strength cover glass or
glass-ceramic article is then further strengthened (e.g.,
chemically), the resultant strength can be higher than that of a
cover glass or glass-ceramic article with a surface that has been
lapped and polished. Down-drawn cover glass or glass-ceramic
articles may be drawn to a thickness of less than about 2 mm. In
addition, down-drawn cover glass or glass-ceramic articles have a
very flat, smooth surface that can be used in its final application
without costly grinding and polishing. Where the cover glass or
glass-ceramic article is a glass ceramic, the cover glass or
glass-ceramic article formed from the down-draw process may be
subjected to a ceramming process by which one or more crystalline
phases are generated.
The fusion draw process, for example, uses a drawing tank that has
a channel for accepting molten glass raw material. The channel has
weirs that are open at the top along the length of the channel on
both sides of the channel. When the channel fills with molten
material, the molten glass overflows the weirs. Due to gravity, the
molten glass flows down the outside surfaces of the drawing tank as
two flowing glass films. These outside surfaces of the drawing tank
extend down and inwardly so that they join at an edge below the
drawing tank. The two flowing glass films join at this edge to fuse
and form a single flowing cover glass article. The fusion draw
method offers the advantage that, because the two cover glass films
flowing over the channel fuse together, neither of the outside
surfaces of the resulting cover glass article comes in contact with
any part of the apparatus. Thus, the surface properties of the
fusion drawn cover glass article are not affected by such contact.
Where the cover glass or glass-ceramic article is a glass ceramic,
the cover glass or glass-ceramic article formed from the fusion
process may be subjected to a ceramming process by which one or
more crystalline phases are generated.
The slot draw process is distinct from the fusion draw method. In
slot draw processes, the molten raw material glass is provided to a
drawing tank. The bottom of the drawing tank has an open slot with
a nozzle that extends the length of the slot. The molten glass
flows through the slot/nozzle and is drawn downward as a continuous
cover glass article and into an annealing region. Where the cover
glass or glass-ceramic article is a glass ceramic, the cover glass
article formed from the slot draw process may be subjected to a
ceramming process by which one or more crystalline phases are
generated.
In some embodiments, the cover glass article may be formed using a
thin rolling process, as described in U.S. Pat. Nos. 8,713,972,
9,003,835, U.S. Patent Publication No. 2015/0027169, and U.S.
Patent Publication No. 20050099618, the contents of which are
incorporated herein by reference in their entirety. More
specifically the cover glass or glass-ceramic article may be formed
by supplying a vertical stream of molten glass, forming the
supplied stream of molten glass or glass-ceramic with a pair of
forming rolls, maintained at a surface temperature of about
500.degree. C. or higher or about 600.degree. C. or higher, to form
a formed cover glass ribbon having a formed thickness, sizing the
formed ribbon of glass with a pair of sizing rolls, maintained at a
surface temperature of about 400.degree. C. or lower to produce a
sized glass ribbon having a desired thickness less than the formed
thickness and a desired thickness consistency. The apparatus used
to form the cover glass ribbon may include a glass feed device for
supplying a supplied stream of molten glass; a pair of forming
rolls maintained at a surface temperature of about 500.degree. C.
or higher, the forming rolls being spaced closely adjacent each
other, defining a glass forming gap between the forming rolls with
the glass forming gap located vertically below the glass feed
device for receiving the supplied stream of molten glass and
thinning the supplied stream of molten glass between the forming
rolls to form a formed glass ribbon having a formed thickness; and
a pair of sizing rolls maintained at a surface temperature of about
400.degree. C. or lower, the sizing rolls being spaced closely
adjacent each other, defining a glass sizing gap between the sizing
rolls with the cover glass sizing gap located vertically below the
forming rolls for receiving the formed cover glass ribbon and
thinning the formed cover glass ribbon to produce a sized cover
glass ribbon having a desired thickness and a desired thickness
consistency.
In some instances, the thin rolling process may be utilized where
the viscosity of the glass does not permit use of fusion or slot
draw methods. For example, thin rolling can be utilized to form the
cover glass or glass-ceramic articles when the glass exhibits a
liquidus viscosity less than 100 kP. The cover glass or
glass-ceramic article may be acid polished or otherwise treated to
remove or reduce the effect of surface flaws.
In contemplated embodiments, the cover glass or glass-ceramic sheet
or article discussed herein has a composition that differs by side
surface. On one side of the cover glass or glass-ceramic sheet 500,
an exemplary composition is: 69-75 wt. % SiO.sub.2, 0-1.5 wt. %
Al.sub.2O.sub.3, 8-12 wt. % CaO, 0-0.1 wt. % Cl, 0-500 ppm Fe,
0-500 ppm K, 0.0-4.5 wt. % MgO, 12-15 wt. % Na.sub.2O, 0-0.5 wt. %
SO.sub.3, 0-0.5 wt. % SnO.sub.2, 0-0.1 wt. % SrO, 0-0.1 wt. %
TiO.sub.2, 0-0.1 wt. % ZnO, and/or 0-0.1 wt. % ZrO.sub.2. On the
other side of the cover glass or glass-ceramic sheet or article
discussed herein an exemplary composition is: 73.16 wt. %
SiO.sub.2, 0.076 wt. % Al.sub.2O.sub.3, 9.91 wt. % CaO, 0.014 wt. %
Cl, 0.1 wt. % Fe.sub.2O.sub.3, 0.029 wt. % K.sub.2O, 2.792 wt. %
MgO, 13.054 wt. % Na.sub.2O, 0.174 wt. % SO.sub.3, 0.001 SnO.sub.2,
0.01 wt. % SrO, 0.01 wt. % TiO.sub.2, 0.002 wt. % ZnO, and/or 0.005
wt. % ZrO.sub.2.
In other contemplated embodiments, composition of the cover glass
or glass-ceramic sheet or article discussed herein includes
SiO.sub.2 55-85 wt. %, Al.sub.2O.sub.3 0-30 wt. %, B.sub.2O.sub.3
0-20 wt. %, Na.sub.2O 0-25 wt. %, CaO 0-20 wt. %, K.sub.2O 0-20 wt.
%, MgO 0-15 wt. %, BaO 5-20 wt. %, Fe.sub.2O.sub.3 0.002-0.06 wt.
%, and/or Cr.sub.2O.sub.3 0.0001-0.06 wt. %. In other contemplated
embodiments, composition of the cover glass or glass-ceramic sheet
or article discussed herein includes SiO.sub.2 60-72 mol. %,
Al.sub.2O.sub.3 3.4-8 mol. %, Na.sub.2O 13-16 mol. %, K.sub.2O 0-1
mol. %, MgO 3.3-6 mol. %, TiO.sub.2 0-0.2 mol. %, Fe.sub.2O.sub.3
0.01-0.15 mol. %, CaO 6.5-9 mol. %, and/or SO.sub.3 0.02-0.4 mol.
%.
EXAMPLES
Apparatus setup--As detailed above, the apparatus comprises three
zones--a hot zone, a transition zone, and a cool or quench zone.
The gaps between the top and bottom thermal bearings (heat sinks)
in the hot zone and the quench zone are set to the desired
spacings. Gas flow rates in the hot zone, transition zone, and
quench zone are set to ensure centering of the glass material,
sheet or part on the air-bearing. The hot zone is pre-heated to the
desired T.sub.0, the temperature from which the glass article will
be subsequently quenched. To ensure uniform heating, cover glass
articles are pre-heated in a separate pre-heating apparatus, such
as a batch or continuous furnace. Generally, cover glass sheets are
pre-heated for greater than 5 minutes prior to loading in the hot
zone. For soda-lime glasses, pre-heating is done around 450.degree.
C. After the pre-heat phase, the cover glass article is loaded into
the hot zone and allowed to equilibrate, where equilibration is
where the glass is uniformly at T.sub.0. T.sub.0 can be determined
by the level of strengthening/tempering desired, but is generally
kept in the range between the softening point and the glass
transition temperature. The time to equilibration is dependent at
least on the thickness of the cover glass. For example, for cover
glass sheets of approximately 1.1 mm or less, equilibration occurs
in approximately 10 seconds. For 3 mm cover glass sheets,
equilibration occurs in approximately 10 seconds to 30 seconds. For
thicker sheets, up to approximately 6 mm, the equilibration time
may be on the order of 60 seconds. Once the cover glass has
equilibrated to T.sub.0, it is rapidly transferred through the
transition zone on air bearings and into the cool or quench zone.
The cover glass article rapidly quenches in the quench zone to a
temperature below the glass transition temperature, Tg. The cover
glass sheet can be maintained in the quench zone for any period of
time from 1 second, 10 seconds, or to several minutes or more,
depending on the degree of quench desired and/or the desired
temperature of the cover glass at removal. Upon removal the cover
glass is optionally allowed to cool before handling.
The following examples are summarized in Table VI.
Example 1
A soda-lime silicate glass plate (e.g., glass comprising at least
70% silicon dioxide by weight, and/or at least 10% sodium oxide by
weight, and/or at least 7% calcium oxide by weight) of 5.7 mm
thickness is pre-heated for 10 minutes at 450.degree. C. before
transferring to the hot zone where it is held at a T.sub.0 of
690.degree. C. for 60 seconds. After equilibrating to T.sub.0, it
is rapidly transferred to the quench zone filled with helium, which
has a gap of 91 m (wherein the gap is the distance between the
surface of the glass sheet and the nearest heat sink), where it is
held for 10 seconds. The resulting article has a surface
compression of -312 MPa, a central tension of 127 MPa, and a
flatness of 83 .mu.m.
Example 2
A soda-lime silicate glass plate of 5.7 mm thickness is pre-heated
for 10 minutes at 450.degree. C. before transferring to the hot
zone where it is held at a T.sub.0 of 690.degree. C. for 60
seconds. After equilibrating it is rapidly transferred to the
quench zone, which has a gap of 91 m, where it is held for 10
seconds. The resulting article has a surface compression of -317
MPa, a central tension of 133 MPa, and a flatness of about 89.7
micrometers.
Example 3
A soda-lime silicate glass plate of 1.1 mm thickness is pre-heated
for 10 minutes at 450.degree. C. before transferring to the hot
zone where it is held at a T.sub.0 of 700.degree. C. for 10
seconds. After equilibrating it is rapidly transferred to the
quench zone filled with helium, which has a gap of 56 .mu.m, where
it is held for 10 seconds. The resulting article has a surface
fictive temperature measured to be 661.degree. C., a surface
compression of -176 MPa, a central tension of 89 MPa, a flatness of
190 .mu.m, and a Vicker's cracking threshold of 10-20 N.
Example 4
A soda-lime silicate glass plate of 0.55 mm thickness is pre-heated
for 10 minutes at 450.degree. C. before transferring to the hot
zone where it is held at a T.sub.0 of 720.degree. C. for 10
seconds. After equilibrating it is rapidly transferred to the
quench zone, which has a gap of 25 m, where it is held for 10
seconds, resulting in an effective heat transfer rate of 0.184
cal/(cm.sup.2-s-.degree. C.). The resulting article has a surface
compression of -176 MPa and a central tension of 63 MPa. Also, the
resulting strengthened articles had a flatness of about 168 (for
the initial 710.degree. C. temperature sample) and 125 micrometers
(for the initial 720.degree. C. temperature sample).
Example 5
A CORNING.RTM. GORILLA.RTM. Glass plate of 1.5 mm thickness is
pre-heated for 10 minutes at 550.degree. C. before transferring to
the hot zone where it is held at a T.sub.0 of 790.degree. C. for 30
seconds. After equilibrating it is rapidly transferred to the
quench zone, which has a gap of 226 .mu.m, where it is held for 10
seconds. The glass article has an improvement in flatness measured
to be 113 .mu.m pre-processing and 58 .mu.m post-processing.
Example 6
A soda-lime silicate glass plate of 0.7 mm thickness is pre-heated
for 10 minutes at 450.degree. C. before transferring to the hot
zone where it is held at a T.sub.0 of 730.degree. C. for 10
seconds. After equilibrating it is rapidly transferred to the
quench zone filled with helium, which has a gap of 31 .mu.m, where
it is held for 10 seconds, resulting in an effective heat transfer
rate of 0.149 cal/(cm.sup.2-s-.degree. C.). The resulting article
has a surface compression of -206 MPa, a central tension of 100
MPa, and a flatness of 82 .mu.m. Upon fracture, the glass sheet is
observed to "dice" (using standard terminology for 2 mm thickness
or greater sheet dicing--i.e., a 5.times.5 cm square of glass sheet
breaks into 40 or more pieces) suggesting that the sheet is fully
tempered.
Example 7
A Borofloat-33 glass plate of 3.3 mm thickness is pre-heated for 10
minutes at 550.degree. C. before transferring to the hot zone where
it is held at a T.sub.0 of 800.degree. C. for 30 seconds. After
equilibrating it is rapidly transferred to the quench zone, which
has a gap of 119 .mu.m, where it is held for 10 seconds. The
resulting article has a flatness of 120 .mu.m. Upon fracture of the
part it is observed to "dice" (using standard terminology for 2 mm
or greater thickness sheet dicing--i.e., a 5.times.5 cm square of
glass sheet breaks into 40 or more pieces) showing that the sheet
is fully tempered.
Example 8
A soda-lime silicate glass plate of 3.2 mm thickness is pre-heated
for 10 minutes at 450.degree. C. before transferring to the hot
zone where it is held at a T.sub.0 of 690.degree. C. for 30
seconds. After equilibrating it is rapidly transferred to the
quench zone, which has a gap of 84 m, where it is held for 10
seconds. The resulting article has a surface compression of -218
MPa, a central tension of 105 MPa, and a flatness of 84 .mu.m.
Example 9
A soda-lime silicate glass plate of 0.3 mm thickness is pre-heated
for 10 minutes at 450.degree. C. before transferring to the hot
zone where it is held at a T.sub.0 of 630.degree. C. for 10
seconds. After equilibrating it is rapidly transferred to the
quench zone, which has a gap of 159 .mu.m, where it is held for 10
seconds. The resulting article has membrane stresses which are
observable by gray field polarimetry, suggesting the glass has
incorporated the thermal stress.
Example 10
A CORNING.RTM. GORILLA.RTM. Glass plate of 0.1 mm thickness is
pre-heated for 10 minutes at 550.degree. C. before transferring to
the hot zone where it is held at a T.sub.0 of 820.degree. C. for 10
seconds. After equilibrating it is rapidly transferred to the
quench zone, which has a gap of 141 .mu.m, where it is held for 10
seconds, resulting in an effective heat transfer rate of 0.033
cal/(cm.sup.2-s-.degree. C.). Upon fracture, the resulting article
displays behavior consistent with a residually stressed glass.
Example 11
A soda-lime silicate glass plate of 1.1 mm thickness is pre-heated
for 10 minutes at 450.degree. C. before transferring to the hot
zone where it is held at a T.sub.0 of 700.degree. C. for 10
seconds. After equilibrating it is rapidly transferred to the
quench zone, which has a gap of 65 .mu.m, where it is held for 10
seconds, resulting in an effective heat transfer rate of 0.07
cal/(cm.sup.2-s-.degree. C.). The resulting article has a surface
fictive temperature measured to be 657.degree. C., a surface
compression of -201 MPa, a central tension of 98 MPa, a flatness of
158 .mu.m, and a Vicker's cracking threshold of 10-20 N.
Example 12
A CORNING.RTM. GORILLA.RTM. Glass plate of 1.1 mm thickness is
pre-heated for 10 minutes at 550.degree. C. before transferring to
the hot zone where it is held at a T.sub.0 of 810.degree. C. for 10
seconds. After equilibrating it is rapidly transferred to the
quench zone which has a gap of 86 .mu.m, where it is held for 10
seconds, resulting in an effective heat transfer rate of 0.058
cal/(cm.sup.2-s-.degree. C.). The resulting article has a surface
fictive temperature measured to be 711.degree. C., a surface
compression of -201 MPa, a central tension of 67 MPa, and a
Vicker's cracking threshold of 20-30 N.
Example 13
A CORNING.RTM. GORILLA.RTM. Glass plate of 1.1 mm thickness is
pre-heated for 10 minutes at 550.degree. C. before transferring to
the hot zone where it is held at a T.sub.0 of 800.degree. C. for 10
seconds. After equilibrating it is rapidly transferred to the
quench zone, which has a gap of 91 .mu.m, where it is held for 10
seconds. The resulting article has a surface fictive temperature
measured to be 747.degree. C., a surface compression of -138 MPa, a
central tension of 53 MPa, a flatness of 66 .mu.m, and a Vicker's
cracking threshold of 20-30 N.
TABLE-US-00006 TABLE VI Thickness Gaps CS CT Flatmaster Fictive
Vickers Example (mm) Composition (um) T.sub.0 Gas (MPa) (MPa) (um)
(.degree. C.) (N) 1 5.7 SLG 91 690 Helium -312 127 83 -- -- 2 5.7
SLG 91 690 Helium -317 133 90 -- -- 3 1.1 SLG 56 700 Helium -176 89
190 661.3 10-20 4 0.55 SLG 25 720 Helium -176 63 125 -- -- 5 1.5 GG
226 790 Helium -- -- 113 before/ -- -- 58 after 6 0.7 SLG 31 730
Helium -206 100 82 -- -- 7 3.3 Borofloat 33 119 800 Helium -- --
121 -- -- 8 3.2 SLG 84 690 Helium -218 105 81 -- -- 9 0.3 SLG 159
630 Helium -- -- -- -- -- 10 0.1 GG 141 820 Helium -- -- -- -- --
11 1.1 SLG 65 700 Helium -201 98 158 657 10-20 12 1.1 GG 86 810
Helium -201 67 -- 711 20-30 13 1.1 GG 91 800 Helium -138 53 66 747
20-30
Additional Example
a 5.7 mm thick sheet of glass comprising at least 70% silicon
dioxide by weight, and/or at least 10% sodium oxide by weight,
and/or at least 7% calcium oxide by weight was run with helium gas
and gaps 204a, 204b (FIG. 21) of about 90 micrometers. The glass
was heated to an initial temperature of about 690.degree. C. and
quickly cooled. The resulting strengthened article had a negative
tensile stress of about 300 MPa on surfaces thereof and a positive
tensile stress of about 121 MPa in the center. Also, the resulting
strengthened article had a flatness of about 106.9 micrometers.
Additional Example
In one experiment using inventive technology disclosed herein, a
1.1 mm thick sheet of glass comprising at least 70% silicon dioxide
by weight, and/or at least 10% sodium oxide by weight, and/or at
least 7% calcium oxide by weight was run with helium gas and gaps
204a, 204b (FIG. 21) of about 160 micrometers. The glass was heated
to an initial temperature of about 680.degree. C. and quickly
cooled. The resulting strengthened article had a negative tensile
stress of about 112 MPa on surfaces thereof and a positive tensile
stress of about 54 MPa in the center. Prior to strengthening, the
sheet of glass had a flatness of about 96 micrometers, but the
resulting strengthened article had a flatness of about 60
micrometers. Accordingly, the strengthening process also flattened
the strengthened glass or glass ceramic article.
Other aspects and advantages will be apparent from a review of the
specification as a whole and the appended claims.
The construction and arrangements of the cover glass and
glass-ceramic, as shown in the various exemplary embodiments, are
illustrative only. Although only a few embodiments have been
described in detail in this disclosure, many modifications are
possible (e.g., variations in sizes, dimensions, structures,
shapes, and proportions of the various elements, values of
parameters, mounting arrangements, use of materials, colors,
orientations) without materially departing from the novel teachings
and advantages of the subject matter described herein. Some
elements shown as integrally formed may be constructed of multiple
parts or elements, the position of elements may be reversed or
otherwise varied, and the nature or number of discrete elements or
positions may be altered or varied. The order or sequence of any
process, logical algorithm, or method steps may be varied or
re-sequenced according to alternative embodiments. Other
substitutions, modifications, changes and omissions may also be
made in the design, operating conditions and arrangement of the
various exemplary embodiments without departing from the scope of
the present inventive technology.
* * * * *
References